Coronavirus (33) mRNA vaccine candidate for COVID-19: mRNA-1273 (part a)

Coronavirus (33) mRNA vaccine candidate for COVID-19: mRNA 1273 (part a)
2. mRNA-1273 vaccine by Moderna
The mRNA vaccine, mRNA-1273, is also called COVID-19 Vaccine Moderna. The vaccine was issued an emergency use authorization by the US Food and Drug Administration for the prevention of COVID-19 on 18th December, 2020. It was the second vaccine approved to be used against COVID-19 in the US.¹ It was also the second mRNA vaccine ever approved to be used in the world. Under the emergency use authorization, individuals 18 years of age or older are allowed to be vaccinated with this mRNA vaccine.

According to the press release from Moderna, approximately 20 million doses will be delivered to the government by the end of December, 2020. The company expects to have between 100 million and 125 million doses available globally in the first quarter of 2021, with 85-100 million of those available in the US.¹ Moderna’s European production capacity is achieved with its strategic manufacturing partner Lonza of Switzerland, and ROVI of Spain for fill-finish services.

The mRNA-1273 is a lipid-nanoparticle (LNP) encapsulated mRNA vaccine expressing the SARS-CoV-2 spike glycoprotein with a transmembrane anchor. The mRNA sequence is modified so that the conformation of the expressed glycoprotein remains stable once it is produced.² The increase in the conformation stability of the expressed glycoprotein triggers production of antibodies with a higher level of specificity. The lipid-nanoparticle capsule of the vaccine composed of four lipids was formulated in a fixed ratio of mRNA and lipid, but the exact ratio is not mentioned.²

The development of the mRNA-1273
It took only 11 months for Moderna, a 10-year biotech startup, to develop the vaccine and finally get the authorization for its use. A major reason for this is the collaboration of the company with various public organizations. The company obtained scientific leadership and clinical trial support from the National Institute of Health (NIH) and the National Institute of Allergy and Infectious Disease (NIAID), and financial support from the Coalition for Epidemic Preparedness Innovations (CEPI) and from the Biomedical Advanced Research and Development Authority (BARDA).¹ The collective effort of private-public partnerships in dealing with the global health crisis is nicely illustrated in this case.

As soon as the SARS-CoV-2 genetic sequence was determined in January 2020, the mRNA-1273 with modified mRNA sequence was then designed and developed by Moderna and the Vaccine Research Center at the NIAID, a part of the NIH.³ In February, NIAID helped to conduct Investigational New Drug (IND)-enabling studies to evaluate potential toxicity risks of the mRNA vaccine prior to human studies.³ Results from a non-human primate preclinical viral challenge study evaluating the vaccine were published in late July.⁴

A Phase 1 study led by NIAID began in mid-March.⁵ Results from the first and the second interim analysis of the Phase 1 study were separately published in mid-July and September respectively.^2,6 Then, on 3rd December, a letter to the editor in The New England Journal of Medicine reported that participants in the Phase 1 study of the Moderna COVID-19 Vaccine still have high levels of neutralizing antibodies 119 days after first vaccination, i.e. 90 days after second vaccination.⁷

The Phase 2 study of the vaccine in the US started on 29th May, and enrolment completed on 8th July.^8,9 This was a placebo-controlled, dose-confirmation study evaluating the safety, reactogenicity* and immunogenicity** of two doses of mRNA-1273 given 28 days apart. Each participant received either a placebo, a 50μg or a 100μg dose at both shots.

The Phase 3 trial of the vaccine, the Coronavirus Efficacy (COVE), was launched in late July 2020. It was a randomized 1:1 placebo-controlled study testing the vaccine at the 100µg dose level in 30,000 participants ages 18 and older in the US. Forty-two percent of total participants in the Phase 3 COVE study were in medically high-risk groups: people aged over 65 and people with chronic diseases such as diabetes, severe obesity and cardiac disease. And although the trial was conducted in America, the study included more than 11,000 participants from diverse communities such as Hispanic or Latin, and Black or African American. The enrolment of Phase 3 COVE Study was completed on 22nd October, 2020.¹⁰ According to the primary efficacy analysis report of the Phase 3 study of 196 cases on the 30th November, the vaccine efficacy against COVID-19 was 94.1%; vaccine efficacy against severe COVID-19 was 100%. The results also suggests a broadly consistent safety and efficacy profile across all evaluated subgroups.

All participants in the COVE study will be continued to be monitored for two years (the duration of the study) to assess long-term protection and safety. Safety data continue to accrue, and the study continues to be monitored by an independent Data Safety Monitoring Board (DSMB) appointed by the NIH.¹



* Reactogenicity refers to reactions (side effects) that occur soon after vaccination, These include both local reactions (such as injection site pain, tenderness, erythema), and systemic reactions (such as fever, headache, myalgia).
* Immunogenecity refers to the ability of human body to provoke an immune response after vaccination.



References
1. Moderna announces FDA authorization of Moderna COVID-19 Vaccine in US. Moderna press release, Dec. 18, 2020. https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-fda-authorization-moderna-covid-19-vaccine-us/
2. L.A. Jackson, E.J. Anderson, N.G. Rouphael, et al. An mRNA vaccine against SARS-CoV-2 — preliminary report. N. Engl. J. Med., 2020; 383:1920-1931. DOI: 10.1056/NEJMoa2022483.
3. Moderna announces funding award from CEPI to accelerate development of messenger RNA (mRNA) vaccine against novel coronavirus. Moderna press release, Jan. 23, 2020. https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-funding-award-cepi-accelerate-development
4. K.S. Corbett, B. Flynn, K.E. Foulds, et al. Evaluation of the mRNA-1273 vaccine against SARS-CoV-2 in nonhuman primates. N. Engl. J. Med., 2020; 383:1544-1555.
5. Moderna announces first participant dosed in NIH-led phase 1 study of mRNA vaccine (mRNA-1273) against novel coronavirus. Moderna press release, March 16, 2020. https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-first-participant-dosed-nih-led-phase-1-study
6. E.J. Anderson, N.G. Rouphael, A.T. Widge, et al. Safety and immunogenicity of SARS-CoV-2 mRNA-1273 vaccine in older adults. N. Engl. J. Med., 2020; 383:2427-2438. DOI: 10.1056/NEJMoa2028436
7. A.T. Widge, N.G. Rouphael, L.A. Jackson, et al. Durability of responses after SARS-CoV-2 mRNA-1273 vaccination. N Engl J Med 2021; 384:80-82. DOI: 10.1056/NEJMc2032195
8. Moderna announces first participants in each age cohort dosed in phase 2 study of mRNA Vaccine (mRNA-1273) against novel coronavirus. Moderna press release, May 29, 2020. https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-first-participants-each-age-cohort-dosed-phase
9. Moderna completes enrolment of phase 2 study of its mRNA vaccine against COVID-19 (mRNA-1273). Moderna press release, July 8, 2020. https://investors.modernatx.com/news-releases/news-release-details/moderna-completes-enrollment-phase-2-study-its-mrna-vaccine
10. Moderna completes enrollment of phase 3 COVE study of mRNA vaccine against COVID-19 (mRNA-1273). Moderna press release, October 22, 2020. https://investors.modernatx.com/news-releases/news-release-details/moderna-completes-enrollment-phase-3-cove-study-mrna-vaccine

Coronavirus (32) mRNA vaccine candidate for COVID-19: BNT162b2 (part b)

Coronavirus (32) mRNA vaccine candidate for COVID-19: BNT162b2 (part b)
After learning about the world's first vaccine approved for use against COVID-19, you may be interested to know more about the two companies, Pfizer Inc. and BioNTech SE, which developed the vaccine. Let us have a look at these two companies in this blog post.

Pfizer Inc.
Pfizer Inc. is one of the world's biggest biopharmaceutical companies and is based in New York. It was established in 1849. The company was started by German-American cousins Charles Pfizer and Charles Erhart in Brooklyn. It started as a manufacturer of fine chemicals. As the company expanded, the headquarters moved to Manhattan in 1868. Later it opened a separate warehouse in Chicago in 1882. An article on the BBC's website thoroughly describes the expansion history of the company from the early days.^1,2

After over 150 years of development, the company is now operating in 180 countries employing 96,000 people. It develops and produces medicines across all therapeutic areas. The research headquarters are in Groton, Connecticut.^2,3

In 2004, Pfizer was added to the Dow Jones stock index, which tracks the 30 large, publicly listed companies trading on the New York Stock Exchange and on NASDAQ.² It had a market value of almost 230 billion dollars on 11th December 2020. Based on the total revenues from the first two quarters of 2020, Pfizer was the world's fifth largest pharmaceutical company, down from the second in 2017.⁴

Pfizer also expanded by acquiring several other pharmaceutical companies. One of these was Warner-Lambert, the original maker of the cholesterol-lowering medicine Lipitor. Since the merger of Warner-Lambert with Pfizer in 2000, Lipitor has contributed billions of revenue and continues to generate roughly US$2 billion per year in sales for Pfizer.⁵

The first pharmaceutical product of the company was santonin, which cured an intestinal parasite common in the 19th century. The drug was a great success as it was given an almond-toffee flavouring to mask its bitterness so that people were more willing to use it for treatment.¹ The company was also known as the world’s first and top producer of vitamin C when they started to mass produce this using a fermentation-free method in 1936. It was also the first company in the world to produce penicillin at a large scale, which was in great demand during World War II.¹ Nowadays, Pfizer's well known products include Advil (Ibuprofen, a non-steroidal anti-inflammatory pain reliever), Lyrica (cholesteral medication), Xanax (psychoactive medicine) and Zoloft (an anti-depressant).³

Despite its successes, the pharmaceutical industry giant has also seen its share of lawsuits and scandals. These included the Protonix case, saying Pfizer failed to warn about the risk of kidney damage; the Prempro lawsuits regarding the onset of breast cancer after using Prempro; the Chantix lawsuits claiming they caused suicidal thoughts and severe psychological disorders; the Depo-Testosterone lawsuits regarding the cause of strokes, blood clots and heart attacks; the Effexor lawsuits which claimed birth defects; the Zoloft lawsuits which also claimed the drug caused birth defects; the Eliquis lawsuits claiming severe bleeding; and the Lipitor lawsuits claiming the development of Type 2 diabetes.³ Some of these lawsuits were dismissed by the court, while others were settled by paying out large sums of money.³

BioNTech SE
This is a biotech company founded in Mainz in Germany in 2008 by a couple, Ugur Sahin and Ozlem Tureci, who are descendants of Turkish immigrants.⁶ Sahin is the CEO of BioNTech, while Tureci, who was a doctor before, is the firm’s chief medical officer. Before starting BioNTech, they set up another biotech company, called Ganymad Pharmaceuticals, focused on immunotherapeutic cancer drugs. That company was sold to Astellas, a Japanese company, for up to 1.3 billion euros in late 2016.⁶

BioNTech, with its North American headquarters in Cambridge, Massachusetts, was publicly traded on the Nasdaq Global Select Market in October 2019. The company was able to generate total gross proceeds of 150 million dollars from that IPO.⁷

A main focus of BioNTech is the use of mRNA as therapeutic strategy. The company has more than a decade of experience in developing their mRNA platforms. Not long after the establishment of the company, they published their first research paper on vaccination of mRNA in preclinical animal models, in 2010.⁸ In more recent years, they put a lot of effort in developing and improving stability of the mRNA and the delivery methods for their therapeutic mRNA platforms.^9-11 Their preclinical studies on the use of mRNA in immunotherapy were at the forefront of the medical research field and are of great value. The results were published in high-ranked peer-reviewed papers, indicating their work is highly recognized by the scientists of the field.^11-14

BioNTech has established a broad set of relationships with multiple global pharmaceutical collaborators, including Eli Lilly and Company, Genmab, Sanofi, Bayer Animal Health, Genentech (a member of the Roche Group), Genevant, Fosun Pharma, and Pfizer. The collaboration with Pfizer started from 2018 when the two companies together developed mRNA vaccines for prevention of influenza.⁶



References
1. Our history. A Journey through Time: How Pfizer has transformed itself and changed the world. Pfizer website in Thai. https://www.pfizer.co.th/en/about-us/%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B8%A7%E0%B8%B1%E0%B8%95%E0%B8%B4%E0%B8%84%E0%B8%A7%E0%B8%B2%E0%B8%A1%E0%B9%80%E0%B8%9B%E0%B9%87%E0%B8%99%E0%B8%A1%E0%B8%B2
2. Pfizer: The making of a global drugs giant. BBC Business, 13 May 2014. https://www.bbc.co.uk/news/business-27309851
3. Drugwatch. https://www.drugwatch.com/manufacturers/pfizer/
4. 10 of the largest pharmaceutical companies by revenue. By Samantha McGrail. Pharma News Intelligence, 16th Oct, 2020. https://pharmanewsintel.com/news/10-of-the-largest-pharmaceutical-companies-by-revenue
5. Lipitor is still churning out billions of dollars. By Bob Herman. Axios, Oct 30, 2019. https://www.axios.com/lipitor-pfizer-drug-patent-sales-2019-6937cdfb-47f1-46bc-8cf0-39e6b88e235e.html
6. What you need to know about BioNTech — the European company behind Pfizer’s Covid-19 vaccine. By Ryan Browne. CNBC Health and Science, Nov 11, 2020. https://www.cnbc.com/2020/11/11/biontech-the-european-company-behind-pfizers-covid-19-vaccine.html
7. Germany's BioNTech raises $150 million in smaller-than-planned U.S. IPO amid market volatility. By Rebecca Spalding and Joshua Franklin. Reuters, 9th October, 2019. https://www.reuters.com/article/us-biontech-ipo-idUSKBN1WO29B
8. S. Kreiter, A. Selmi, M. Diken, et al. 2010. Intranodal vaccination with naked antigen-encoding RNA elicits potent prophylactic and therapeutic antitumoral immunity.Cancer Res., Nov 15; 70(22): 9031-9040
9. J. Kowalska, A. Wypijewska del Nogal, Z.M. Darzynkiewicz, et al. 2014. Synthesis, properties, and biological activity of boranophosphate analogs of the mRNA cap: versatile tools for manipulation of therapeutic relevant cap-dependent process. Nucleic Acids Res. 42(16): 10245-10264.
10. L.M. Kranz, M. Diken, H. Haas, et al. 2016. Systemic RNA delivery to dendritic cells exploits antiviral defense for cancer immunotherapy. Nature. Jun 1; 534(7607): 396-401.
11. S. Grabbe, H. Haas, M. Diken, et al. 2016. Translating nanoparticulate-personalized cancer vaccines into clinical applications: case study with RNA-lipoplexes for the treatment of melanoma. Nanomedicine (Lond). Oct; 11(20): 2723-2734.
12. N. Pardi, M.J. Hogan, R.S. Pelc, et al. 2017. Zika virus protection by a single low-dose nucleoside-modified mRNA vaccination. Nature. Mar 9; 543(7644): 248-251.
13. C.R. Stadler, H. Bähr-Mahmud, L. Celik L, et al. 2017. Elimination of large tumors in mice by mRNA-encoded bispecific antibodies. Nature Medicine Jul; 23(7): 815-817.
14. U. Sahin U, E. Derhovanessian, M. Miller, et al. 2017. Personalized RNA mutanome vaccines mobilize poly-specific therapeutic immunity against cancer. Nature. Jul 13; 547(7662): 222-226.

Coronavirus (31) mRNA vaccine candidate for COVID-19: BNT162b2 (part a)

Coronavirus (31) mRNA vaccine candidate for COVID-19: BNT162b2 (part a)
Continued from my last blog post.
1. BNT162b2 by Pfizer Inc. and BioNTech SE
BNT162b2 was the first COVID-19 vaccine in the world to achieve authorization. The UK regulator, Medicine and Healthcare products Regulatory Agency (MHRA), authorized emergency supply of COVID-19 mRNA vaccine under Regulation 174 on 2nd December.¹ And today, the U.S. Food and Drug Administration (FDA) also granted an Emergency Use Authorization (EUA) to permit the emergency use of the vaccine in individuals that are 16 years old and over.²

The UK has ordered 40 million doses of the vaccine, which is enough to vaccinate 20 million people. The first batch of the mRNA vaccine arrived in the UK on 3rd December from Belgium. By the end of this year, the UK government expects to have 800,000 vaccine doses arrived. The vaccination started on 8th December. According to a suggestion from the Joint Committee on Vaccination and Immunisation (JCVI), the first batch should be given to NHS hospital staff and patients. Care home residents and care home staff are prioritised for vaccination next.³

The vaccination of BNT162b2 is a two-dose regimen, 21 days apart, and administered intramuscularly (injected into a muscle). The vaccine comes in concentrated form and remains stable for 6 months at -80°C to -60°C. Once a vaccine vial is taken out from the freezer and thawed, it will be diluted with sodium chloride 9 mg/mL (0.9%) solution. The diluted, ready to use vaccine should be stored between 2°C and 25°C and used within 6 hours after dilution. Before injection, you can have a look with the nurse to check if the vaccine appears as an off-white solution with no particulates visible. The vaccine cannot be used if particulates or discolouration are present.⁴

You should bear in mind that the protection is not fully effective until at least 7 days after the second dose of the vaccine. Even you are vaccinated, the 94%-95% of efficacy of the vaccine BNT162b2 means that you are not entirely safe from COVID-19. Vaccination with the mRNA vaccine may not protect all recipients.^4-6

It is important to note that the following peoples are not suitable to be vaccinated with BNT162b2:⁴
1. Children under 16 years of age. The safety and efficacy of the vaccine in this age group has not yet been established;
2. Pregnant women. Animal reproductive toxicity studies have not been completed. The vaccine, therefore, is not recommended during pregnancy;
3. Women during breast-feeding. It is unknown whether the mRNA vaccine is excreted in human milk. There may be a risk to newborns and infants;
4. Individuals receiving anti-coagulant therapy, and ones with bleeding disorder. Anti-coagulant therapy and bleeding disorder would contraindicate an intramuscular injection;
5. People with a history of significant allergic reactions. There were reports of allergic reaction shortly after the injection in two NHS workers who have a history of serious allergies and carry adrenaline pens around with them.⁷ MHRA advised that people with a history of significant allergic reactions should not have the mRNA vaccination.⁴

Moreover, it should be bourne in mind that if you are of childbearing age, you should avoid pregnancy for at least 2 months after the second shot. And if you are currently suffering from acute severe febrile illness, the administration of the mRNA vaccine should be postponed.⁴

The development of BNT162b2
The vaccine was first developed by BioNTech. Pfizer later joined (in March) to accelerate the development programme, which initially included 4 vaccine candidates. Three vaccine candidates represent a different combination of mRNA format, either a uridine containing mRNA or nucleoside modified mRNA, and target antigen: either the larger spike sequence of SARS-CoV-2 or the smaller optimized receptor binding domain (RBD) from the spike protein. The fourth vaccine candidate contains self-amplifying mRNA. Each mRNA format is combined with a lipid-nanoparticle (LNP) formulation.^8,9

The pre-clinical studies on the four mRNA vaccine candidates was completed in Germany in April.⁹ Two vaccine candidates, BNT162b1 and BNT162b2, induced high viral antigen specific CD4+ and CD8+T cell responses, and high levels of neutralizing antibody in various animal species. They offered protective effects in Rhesus macaques from SARS-CoV-2 infection. The study result on the vaccine candidate BNT162b2 was available to the public in September.¹⁰

The first clinical trial of the vaccine candidates started on 23rd April in Germany (NCT04380701; EudraCT: 2020-001038-36) and later in the US (NCT04368728; C4591001).¹¹ The initial clinical trial included dose range studies, aiming to determine the optimal dose for the mRNA vaccine candidates, as well as to evaluate the safety and immunogenicity of the vaccines. Pfizer took care of clinical trials in the US and other countries other than Germany, while BioNTech conducted its own trials in Germany.

Among the four mRNA vaccine candidates, BNT162b1, a lipid-nanoparticle (LNP)-formulated nucleoside-modified mRNA that encodes the SARS-CoV-2 receptor binding domain (RBD) from the spike protein, and BNT162b2, a LNP-formulated nucleoside-modified mRNA that encodes the spike glycoprotein of SARS-CoV-2, were chosen to be evaluated in the phase 1/2 clincial trials. Both vaccine candidates demonstrated a manageable tolerability at dose levels that elicited robust immune responses. However, BNT162b2 was found to have a milder reactogenicity profile. Based on the preclinical and clinical data obtained in phase 1/2 studies, BNT162b2 was chosen to enter into phase 2/3 study at a 30µg dose level in a 2 dose regimen.^12-14

The information published in November shows that BNT162b2 is now in phase 3 clinical trials in the US, Germany, Argentina, Brazil, South Africa, and Turkey. A pharmaceutical company from China, Fosun Pharma, jointly conducted phase 2 clinical trials in Jiangsu, China with BioNTech in November.¹⁵

Safety results
The safety of BNT162b2 was evaluated in participants 16 years of age and older in two clinical studies. Study EudraCT: 2020-001038-36 enrolled 60 participants in Germany aged between 18 and 55. Study C4591001 enrolled approximately 44,000 participants of aged 12 or older, in the US, Turkey, South Africa, and South America.

In a group of age 16 and above in Study C4591001, a total of 21,720 participants received at least one dose of BNT162b, and 21,728 participants received a placebo. Out of these, at the time of the analysis, 19,067 participants (9531 who received BNT162b2 and 9536 who received the placebo) were evaluated for safety, two months after the second dose. The first interim report of the phase 3 study was published in November.^5,6

The most frequent adverse reactions in participants aged 16 years and older were pain at the injection site (>80%), fatigue (>60%), headache (>50%), myalgia (>30%), chills (>30%), arthralgia (>20%) and pyrexia (>10%). The reactions were usually mild or moderate in intensity and resolved within a few days after vaccination.⁴

There was no pause of study in the clinical trials for the mRNA vaccine BNT162b2, and no report of hospitalization or death after the vaccination in the clinical trials.

Pre-order agreement
Since the mRNA vaccine candidates entered the clinical trial, Pfizer and BioNTech have signed supply agreements with different countries to deliver millions of doses of the vaccine if approved. The companies signed agreements in July to deliver up to 600 million doses of their vaccine for COVID-19 to the US (enough for 2 per person for nearly the whole population), and 120 million doses to Japan.^16,17 In August, the companies signed agreements to provide the mRNA vaccine to Canada.¹⁸ The European Union also signed a contract in November with the two companies to provide the EU with 200 million doses of the mRNA-based vaccine.¹⁹ Today, BioNTech announced an agreement to supply Mainland China with an initial 100 million doses of their mRNA-based vaccine candidate.¹⁵ According to the press release from Pfizer, they have the goal of manufacturing globally up to 50 million doses by the end of 2020 and approximately 1.3 billion doses by the end of 2021.⁶

BioNTech received an up-front payment of $185 million, including an equity investment of approximately $113 million, from Pfizer, upon the collaboration to develop an mRNA vaccine with BioNTech. The company will be eligible to receive further payments of up to $563 million for a potential total consideration of $748 million.⁸



References
1. Decision: Regulatory approval of Pfizer/BioNTech vaccine for COVID-19. Gov.UK news release, 2nd Dec., 2020. https://www.gov.uk/government/publications/regulatory-approval-of-pfizer-biontech-vaccine-for-covid-19
2. FDA takes key action in fight against COVID-19 by issuing emergency use authorization for first COVID-19 vaccine. FDA news release, 11th Dec., 2020. https://www.fda.gov/news-events/press-announcements/fda-takes-key-action-fight-against-covid-19-issuing-emergency-use-authorization-first-covid-19
3. Covid-19: UK 'confident' of having 800,000 vaccine doses by next week. BBC news, 6th Dec., 2020. https://www.bbc.co.uk/news/uk-55184849
4. Information for healthcare professionals on Pfizer/BioNTech COVID-19 vaccine. MHRA website, 10th Dec., 2020. https://www.gov.uk/government/publications/regulatory-approval-of-pfizer-biontech-vaccine-for-covid-19/information-for-healthcare-professionals-on-pfizerbiontech-covid-19-vaccine
5. Pfizer and BioNTech announce vaccine candidate against COVID-19 achieved success in first interim analysis from phase 3 study. Pfizer press release, 9th Nov., 2020. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-announce-vaccine-candidate-against
6. Pfizer and BioNTech conclude phase 3 study of COVID-19 vaccine candidate, meeting all primary efficacy endpoints. Pfizer press release, 18th Nov., 2020. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-conclude-phase-3-study-covid-19-vaccine
7. Covid-19 vaccine: Allergy warning over new jab. By Nick Triggle and Rachel Schraer. BBC News, 9th Nov., 2020. https://www.bbc.co.uk/news/health-55244122
8. Pfizer and BioNTech to co-develop potential COVID-19 vaccine. Pfizer press release, 17th March, 2020. https://www.pfizer.co.uk/pfizer-and-biontech-co-develop-potential-covid-19-vaccine/
9. BioNTech and Pfizer announce regulatory approval from German authority Paul-Ehrlich-Institut to commence first clinical trial of COVID-19 vaccine candidates. Pfizer press release, 22nd April, 2020. https://www.pfizer.com/news/press-release/press-release-detail/biontech_and_pfizer_announce_regulatory_approval_from_german_authority_paul_ehrlich_institut_to_commence_first_clinical_trial_of_covid_19_vaccine_candidates
10. A.B. Vogel, I. Kanevsky, Y. Che, et al. A prefusion SARS-CoV-2 spike RNA vaccine is highly immunogenic and prevents lung infection in non-human primates. BioRxiv, Sept. 08, 2020. doi: https://doi.org/10.1101/2020.09.08.280818
11. BioNTech and Pfizer announce completion of dosing for first cohort of phase 1/2 trial of COVID-19 vaccine candidates in Germany. Pfizer press release, 29th April, 2020. https://www.pfizer.com/news/press-release/press-release-detail/biontech-and-pfizer-announce-completion-dosing-first-cohort
12. U. Sahin, A. Muik, E. Derhovanessian, et al. COVID-19 vaccine BNT162b1 elicits human antibody and TH1 T cell responses. Nature, 2020;586, 594–599.
13. E.E. Walsh, R.W. Frenck, A.R. Falsey, et al. Safety and immunogenicity of two RNA-based Covid-19 vaccine candidates. N. Engl. J. Med., 2020 Dec 17;383(25):2439-2450. doi: 10.1056/NEJMoa2027906. Epub 2020 Oct 14.
14. Pfizer and BioNTech choose lead mRNA vaccine candidate against COVID-19 and commence pivotal phase 2/3 global study. Pfizer press release, 27th July, 2020. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-choose-lead-mrna-vaccine-candidate-0
15. BioNTech and Fosun Pharma to supply China with mRNA-based COVID-19 vaccine. BioNTech press release, 16th Dec., 2020. https://investors.biontech.de/news-releases/news-release-details/biontech-and-fosun-pharma-receive-approval-commence-covid-19/
16. Pfizer and BioNTech announce an agreement with U.S. Government for up to 600 million doses of mRNA-based vaccine candidate against SARS-CoV-2. Pfizer press release, 22nd July, 2020. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-announce-agreement-us-government-600
17. Pfizer and BioNTech to supply Japan with 120 million doses of their BNT162 mRNA-based vaccine candidate. Pfizer press release, 31st July, 2020. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-supply-japan-120-million-doses-their
18. Pfizer and BioNTech to supply Canada with their BNT162 mRNA-based vaccine candidate. Pfizer press release, 5th August, 2020. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-supply-canada-their-bnt162-mrna-based
19. Pfizer and BioNTech reach an agreement to supply the EU with 200 million doses of their BNT162b2 mRNA-based vaccine candidate against SARS-CoV-2. Pfizer press release, 11th Nov., 2020. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-reach-agreement-supply-eu-200-million

Coronavirus (30) mRNA vaccine for COVID-19: an introduction

Coronavirus (30) mRNA vaccine for COVID-19: an introduction
The UK's Medicines and Healthcare Products Regulatory Agency (MHRA) announced on 2nd November that they have granted authorisation for temporary supply of COVID-19 mRNA vaccine BNT162b2, from Pfizer and BioNTech, for active immunization of individuals aged 16 years old and over.¹ This is the first vaccine receiving approval to be used for COVID-19 prevention in the UK. It is one of the mRNA vaccines which had entered Phase 3 according to the WHO's data.² In this blog post, I am going to introduce you the mRNA vaccines.

What is an mRNA vaccine?
Conventional vaccines work by injecting either a dead form of the pathogen (for inactivated vaccines), or a weakened form of it (for live attenuated vaccines), into the body to trigger the production of antibodies against the pathogen. You may wonder how the pathogen can trigger the immune system. A portion of the pathogen called the antigen binds to B-cell surfaces and stimulates these B cells to divide and mature into a group of identical cells, called specific antibodies, that can recognize the antigen. Therefore the antigen, the portion of the new infectious agent—but not the whole infectious agent—initiates our immunity to recognize the pathogen and respond to it. Once the immunity against the pathogen is built, our immune system can respond quickly next time the same pathogen invades.

Based on this understanding of how human immunity against pathogens works, scientists recently developed the mRNA vaccine, which produces only an antigen that inititates specific antibody production and not the rest of the pathogen.³ According to Pfizer's website introducing mRNA vaccines, "mRNA vaccines work by introducing into the body a messenger RNA (mRNA) sequence that contains the genetic instructions for the vaccinated person’s own cells to produce the vaccine antigens and generate an immune response."⁴

The mRNA sequence for the mRNA vaccines are synthetic oligonucleotides*. Since mRNA is not very stable, the genetic materials include modified nucleosides to prevent degradation.⁵ Moreover, mRNA is highly vulnerable to degradation by enzymes, called extracellular RNases, in our body. Therefore, mRNAs of the mRNA vaccines are usually encapsulated within lipids or polymeric nanoparticles to protect the mRNAs and to enable entry of the mRNA into cells. These carrier systems are designed to protect mRNA from enzymes' degradation and also allow rapid uptake of the mRNA by human cells.^3,6 Recent technology innovations, especially in nanotechnology, enables the synthesis of mRNA molecules with higher stability and the encapsulation of mRNA molecules in nanoparticles for efficient delivery of mRNA into target cells.⁵

Additionally, in order to provoke a stronger immune response, a booster shot is usually added after the first shot of the mRNA vaccine. The two mRNA vaccine candidates for COVID-19 that have entered phase 3 clinical trials both require 2 doses.

Advantages of mRNA vaccines over conventional vaccines
1. Faster and cheaper to produce: The process of producing mRNA is inexpensive, and could be standardised and scaled easily. This allows quick responses to large outbreaks and epidemics.³
2. Higher efficacy: There is no viral vector to carry mRNA, therefore the anti-vector immunity, which could decrease the efficacy of the vaccine, is avoided. Additionally, as there is no fear of anti-vector immunity, mRNA vaccines can be administered repeatedly.³
3. Safer: mRNA vaccine does not contain any viral component, neither inactivated disease-causing organisms or proteins made by pathogen. Thus there is no potential risk of infection or insertional mutagenesis. Moreover, mRNA is degraded by normal cellular processes, and its in vivo half-life can be regulated through the use of various modifications and delivery methods. The inherent immunogenicity of the mRNA can be down-modulated to further increase the safety profile.³

However, since mRNA vaccine is a new type of vaccine developed by new technology, it has never before been applied clinically. It is now too early to say the vaccine is totally safe. Long-term follow-up over many years on the people who have used mRNA vaccines is necessary to find out if there are any long-term side effects of this type of vaccine.

Both of the mRNA vaccine candidates for COVID-19 contain genetic codes for the Spike glycoprotein of SARS-CoV-2. My next two blog posts will take a closer look at the two mRNA vaccine candidates.



*Synthesized oligonucleotides are short fragments of nucleic acids with defined chemical structure manufactured by biotech companies. The technique of synthesizing oligonucleotides is very useful, as it provides a convenient and inexpensive way to produce custom-made fragments of nucleic acids with desired sequences.



References
1. Decision: Regulatory approval of Pfizer/ BioNTech vaccine for COVID-19. Gov.UK’s news release, 2nd Dec, 2020. https://www.gov.uk/government/publications/regulatory-approval-of-pfizer-biontech-vaccine-for-covid-19
2. Draft landscape of COVID-19 candidate vaccines. World Health Orgainzation. https://www.who.int/publications/m/item/draft-landscape-of-covid-19-candidate-vaccines
3. N. Pardi, M.J. Hogan, F.W. Porter, et al. mRNA vaccines — a new era in vaccinology. Nat. Rev. Drug Discov. 2018 Apr; 17(4):261-279.
4. Behind the science: what is an mRNA vaccine? Pfizer's website. https://www.pfizer.co.uk/behind-science-what-mrna-vaccine
5. K. Kariko, H. Muramatsu, F.A. Welsh, et al. Incorporation of pseudouridine into mRNA yields superior nonimmunogenic vector with increased translational capacity and biological stability. Mol. Ther., 2008, 16(11), 1833–1840.
6. How nanotechnology helps mRNA Covid-19 vaccines work. By Elizabeth Cooney. STAT Biotech, 1st Dec., 2020. https://www.statnews.com/2020/12/01/how-nanotechnology-helps-mrna-covid19-vaccines-work/

Coronavirus (29) Pre-existing immunity to adenovirus type 5 and type 26

Coronavirus (29) Pre-existing immunity to adenovirus type 5 and type 26
In my last blog post, I mentioned that previous infection by a human adenovirus could decrease the efficacy of vaccines that use that adenovirus as a backbone. The best way to avoid using adenovirus vaccines that we may be immune to, is to use a viral vectored vaccine with a non-human adenovirus vector, like the AZD1222 by AstraZeneca and Oxford University, which uses chimpanzee adenovirus. Human populations around the world have a much lower level of pre-existing immunity to the chimpanzee adenovirus.

Alternatively, we can check our serum antibody levels to the adenovirus. However, as most of us are not virology or vaccine experts, we won’t know what is an acceptable level of neutralizing antibodies against the adenovirus used by the vaccine we are thinking of taking.

There were studies performed to check the pre-existing immunity to Adenovirus type 5 (Ad5) and Adenovirus type 26 (Ad26), the two common human adenoviruses used by the adenovirus vectored vaccines for COVID-19, in different populations, by testing the serum neutralizing antibodies to the two adenoviruses. I have put together the data from two of the studies into the table below.^1-2 Looking at this data may give us an idea of which type of vaccine to use, if we were given a choice.

Infection rate of Ad5 and Ad26 in different populations
Country	Seroprevalence of Ad5 (%)	Seroprevalence of Ad26 (%)
China	73.12	35.32
Kenya	90.51	66.21
South Africa	87.9-89.51	43.1–53.21
Thailand	82.21	54.61
Uganda	86.41	67.81
United States	~401	~121

As we can see from the table, Ad5 infection is generally more common than Ad26 in all the nations studied. The infection rate of Ad5 is at least 50% higher than that of Ad26. Moreover, people in the developing world seems to have higher adenovirus infection rate. Detailed data (not shown in this table) from the results of the multinational study¹ also showed a much higher proportion of people with high level of blood antibody against Ad5 in the high Ad5 prevalence areas, in contrast to markedly fewer individuals in these regions demonstrating a high level of blood antibody to Ad26.¹ Data also showed that the median level of blood antibody to Ad26 in the 4381 international test participants was approximately 10-fold lower than the median level of blood antibody to Ad5.

The data from the studies did not include populations from all countries around the world, and the studies were done at least 7 years ago. I cannot find any more up-to-date data on studies comparing the prevalence of Ad5 and Ad26 infections. However, the above data gives us a general idea that people in developing countries should try to avoid using Ad5 vectored vaccines. If we were given a chance to choose from either Ad5 or Ad26 vectored vaccines, we should choose Ad26, as we have a lower chance of having a pre-existing immunity against the Ad26, and the blood level of neutralizing antibody to Ad26 is much lower even if we have been infected by Ad26. A low blood level of neutralizing antibody to Ad26 was shown not to reduce the efficacy of vaccines using Ad26.¹

Before developing viral vectored vaccines, Harvard Medical school undertook a thorough study on the epidemiology of Ad5 and Ad26 in populations of several nations.¹ This study gave them sufficient ground to use Ad26 for their viral vectored vaccines. Therefore, we should have confidence on the efficacy of the vaccine co-developed by the Harvard Medical School and Janssen Pharmaceuticals, which uses Ad26 as a backbone. The vaccine Sputnik V by Gamaleya Research Centre uses Ad5 and Ad26 in the different shots for their 2-shot regimen. The use of Ad26 in one of their vaccines certainly helps to overcome the pre-existing immunity to Ad5 which diminishes the effecacy of the vaccine. On the other hand, the COVID-19 vaccine developed by CanSino uses Ad5 as the vaccine’s backbone; it will be a big challenge for them to market this vaccine to areas with high baseline Ad5 neutralizing antibodies.³



References
1. D.H. Barouch, S.V. Kik, G.J. Weverling, et al. International seroepidemiology of adenovirus serotypes 5, 26, 35, and 48 in pediatric and adult populations. Vaccine. 2011; 29: 5203-5209.
2. S. Zhang, W. Huang, X. Zhou, et al. Seroprevalence of neutralizing antibodies to human adenoviruses type-5 and type-26 and chimpanzee adenovirus type-68 in healthy Chinese adults. J. Med. Virol., 2013 Jun;85(6):1077-84.
3. A big obstacle: Where can CanSino test its vaccine abroad? By Roxanne Liu, and Miyoung Kim. Reuters, July 30, 2020.

Coronavirus (28) Non-replicating viral vector vaccine candidates for COVID-19 (part e)

Coronavirus (28) Non-replicating viral vector vaccine candidates for COVID-19 (part e)
AstraZeneca announced interim results for their phase 3 single-blinded, multi-centre, randomised, controlled studies from the UK (COV002) and Brazil (COV003) yesterday.¹ Participants were randomized to receive intramuscular injection with either a half-dose/full-dose regimen (n=2,741) or two-full-doses regimen of AZD1222 (n=8,895), or a placebo using meningococcal conjugate vaccine called MenACWY or saline. Two shots were injected, at least one month apart.

By the end of the study, among a total of 22,690 participants, 131 were found to be COVID-19 positive: of these, 101 had received placebo, 3 had received half-dose/full-dose regimen, and 27 had received full dose at both initial and later shot. This led to the initial statistics of 90% vaccine efficacy when AZD1222 was given as half-dose/full-dose regimen, and 62% efficacy for the full-dose/full-dose regimen. On average, this showed a 70% effectiveness rate of the vaccine at preventing the COVID-19. Vaccine offering protection over 50% of vaccinated people is considered to be efficacious.^# Moreover, no serious safety events related to the vaccine were reported in the studies.^2,3

Professor Andrew Pollard, Director of the Oxford Vaccine Group and Chief Investigator of the Oxford Vaccine Trial, said these findings show that they “have an effective vaccine that will save many lives.” If the half-dose/full-dose regimen does give 90% effectiveness, they will apply this dosing regimen, and this means that “more people could be vaccinated with planned vaccine supply.”³ That seems to be good news.

As we are approaching the end of the year, more results from phase 3 studies of candidate vaccines are coming out, and also we have more informations about their prices. The vaccine made of non-replicating viral vector can be kept in a conventional fridge (2°C-8°C), similar to inactivated vaccines. Once a non-replicating viral vectored vaccine is produced, it can be stored, transported and handled at normal refrigerated conditions for at least six months, and can be administered within existing healthcare facilities. The transportation is easier and thus the cost is lower than the ones that require ultra-low temperatures. According to a Healthline online article, AstraZeneca’s two-dose vaccine could be just US $3 to $4 per dose, while each dose for Johnson & Johnson’s two-dose vaccine will cost about US $10.⁴ Meanwhile, the Russian Gamaleya Centre announced that the cost of their two-dose Sputnik V vaccine will be less than US $10 per dose for international markets.⁵ No information on the cost of the adenoviral vectored vaccine candidate by CanSinoBio can be found yet.

The ease of storage and handling, and the lower prices, render the non-replicating viral vectored vaccines viable for use in resource-limited countries. Moreover, such vaccines provide long-term gene expression, and high specificity of gene delivery to target cells. Additionally, since viral vectored vaccines result in endogenous antigen production, both humoral* and cellular immune** responses are stimulated. In other words, viral vectored vaccine triggers high immunogenicity.⁶

With all these advantages of using viral vectors, we should however not ignore some of the factors that may diminish the effectiveness of the vaccine candidates.

All four viral-vectored vaccines that entered phase 3 clinical trials use Adenovirus as a vector. Adenoviral DNA has the advantage of not integrating into the human genome and not being replicated during cell division. Apart from AstraZenica’s AZD1222 which used adenovirus ChAdOx1 (which causes the common cold in chimpanzees), the other 3 vaccine candidates use human adenoviruses, either Adenovirus type 5 (Ad5) or type 26 (Ad26), which have been genetically modified, as carriers of the genetic sequence that produces the Spike glycoprotein of SARS-CoV-2. However, a significant number of people may have already been infected with these human adenoviruses, and neutralising antibodies to the viral vectors already exist in these infected populations. These neutralising antibodies can inactivate the virus before it can reach the target cells, and thus decrease its efficacy.⁷

In fact, the baseline of different human adenovirus infections varies from place to place globally. The population with a higher baseline of pre-existing Ad26 infection, for example, is expected to have a lower immunity response upon the first dose of Sputnik V vaccine from Gamaleya Centre in Russia, or Ad26.COV2.S vaccines from Janssen Pharmaceuticals etc. Therefore when we consider which viral vectored vaccine to use, we should check the infection rate of the particular adenovirus in our population and try to avoid using a vaccine that contains an adenovirus that is already widespread in our area.

Also, people who volunteered to receive viral vector vaccines in previous clinical trials should also be aware not to rely on viral vectored vaccines for COVID-19 that use the same adenovirus carrier as they were administered in the previous trial.

Recombinant adenovirus vectors have been developed since the 1980s. Gamaleya Research Institute used Ad5 to produce vaccines against Ebola that were approved for use in 2015 and 2020.⁸ Another vaccine by Janssen Pharmaceuticals for Ebola, which was approved in 2020 by the European Union, used Ad26.⁹ The long-term effect of the use of these viral vectored vaccines is still unknown. However, the use of Ad5 as a carrier in an HIV vaccine candidate did increase the possibility of transmission of HIV.¹⁰ Moreover, the reports of neurological conditions, including multiple sclerosis and transverse myelitis, during the clinical trials of AstraZeneca's vaccine candidate,¹¹ also raises concern for the safety of adenoviral vectored vaccines.<sup>12



#</sup>US Food and Drug Administration Coronavirus (COVID-19) update: FDA takes action to help facilitate timely development of safe, effective COVID-19 vaccines. June 30, 2020. https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-takes-action-help-facilitate-timely-development-safe-effective-covid
*Humoral immune responses protect extracellular spaces of the body from bacterial infections. Antibodies produced by B cells cause the destruction of extracellular microorganisms and prevent the spread of intracellular infections. (Immunobiology: The Immune System in Health and Disease. 5th edition. Chapter 9, The Humoral Immune Response. https://www.ncbi.nlm.nih.gov/books/NBK10752/)
** Cellular immune response is a protective immune process that involves the activation of phagocytes, antigen-sensitized cytotoxic T cells, and the release of cytokines and chemokines, in response to antigens. (Definition from Nature research. https://www.nature.com/subjects/cellular-immunity)





References
1. AZD1222 vaccine met primary efficacy endpoint in preventing COVID-19. AstraZeneca press release, 23rd November 2020. https://www.astrazeneca.com/media-centre/press-releases/2020/azd1222hlr.html
2. Covid-19: Oxford University vaccine is highly effective. By James Gallagher. BBC news, 23rd November, 2020. https://www.bbc.co.uk/news/health-55040635
3. Oxford University breakthrough on global COVID-19 vaccine. Press release of University of Oxford, 23rd November, 2020. https://www.research.ox.ac.uk/Article/2020-11-23-oxford-university-breakthrough-on-global-covid-19-vaccine
4.https://www.healthline.com/health-news/how-much-will-it-cost-to-get-a-covid-19-vaccine#How-much-each-dose-will-cost
5. The cost of one dose of the Sputnik V vaccine will be less than $10 for international markets. Press release from Gamaleya Center, 24th November, 2020. https://sputnikvaccine.com/newsroom/pressreleases/the-cost-of-one-dose-will-be-less-than-10-for-international-markets/
6. Debby van Riel and Emmie de Wit. Next generation vaccines platform for COVID-19. Nature Materials, 2020, vol. 19, 810–820.
7. CanSino’s, J&J’s Covid-19 vaccines may be stifled by pre-existing antibodies while AstraZeneca’s, ReiThera’s may need booster. 23rd June 2020. ClinicalTrials Arena, https://www.clinicaltrialsarena.com/comment/covid-19-vaccines-antibodies-booster/
8. https://sputnikvaccine.com/about-us/
9. J&J receives EU approval for Ebola vaccine. By Ben Hargreaves. Biopharma Reporters, 6th July, 2020. https://www.biopharma-reporter.com/Article/2020/07/06/Janssen-Ebola-vaccine-gets-European-approval
10. S.P. Buchbinder, M.J. McElrath, C. Dieffenbach, et al. Use of adenovirus type-5 vectored vaccines: a cautionary tale. Lancet, 2020, Oct 31; 396 (10260): E68-E69.
11. AstraZeneca’s quick Covid-19 vaccine trial restart splits experts. ClinicalTrials comment, Global Data Healthcare, last updated October 12th, 2020. https://www.clinicaltrialsarena.com/comment/azd1222-covid-vaccine-trials-astrazeneca/
12. J&J pause adds to adenovirus vaccine doubts. By Madeleine Armstrong. Evaluate Vantage, 13th Oct, 2020. https://www.evaluate.com/vantage/articles/news/jj-pause-adds-adenovirus-vaccine-doubts

Coronavirus (27) Non-replicating viral vectored vaccine candidates for COVID-19 (part d)

Coronavirus (27) Non-replicating viral vector vaccine candidates for COVID-19 (part d)
Continued from my last blog post.
4.Ad26.COV2.S by Janssen Pharmaceutical Companies
The development of the vaccine candidate Ad26.COV2.S, also named JNJ-78436735, is another example of the collaboration between academia and industry. This vaccine was jointly developed by scientists from Janssen Pharmaceutical Companies and a leading virology and vaccine laboratory led by Dan Barouch, M.D., Ph.D. in the Beth Israel Deaconess Medical Center, Harvard Medical School.¹

The name of the vaccine candidate, Ad26.COV2.S, tells us that it is basically an adenovirus type 26 viral vector expressing the Spike (S) protein of SARS-CoV-2. Janssen Pharmaceuticals and the team led by Dan Barouch started working on developing the vaccine for COVID-19 since January. At the end of March, Ad26.COV2.S was then identified, among other constructs, to be efficacious.²

It was found that a single dose of Ad26.COV2.S was able to elicit strong immune responses in rhesus macaques. None of the vaccinated animals had detectable viral loads in bronchoalveolar lavage upon infection with SARS-CoV-2. The detail preclinical data was published in Nature.³

Phase 1/2a
A multi-centre, randomized, double-blind, placebo-controlled phase 1/2a study on Ad26.COV2-S (NCT04436276) started from mid July this year in both the US and Belgium. The study includes 3 cohorts which recruited healthy adults aged 18 to 55 years (cohorts 1a and 1b, 402 participants), as well as adults aged 65 years and older (cohort 3, 403 participants).^4,5 The participants received intramuscular injection of Ad26.COV2-S (at 5x10¹⁰ or 1x10¹¹ viral particles per vaccination, in either one- or two-doses injected 8 weeks apart) or placebo (0.9% saline).

An interim report with data obtained during the first 4 weeks after the first vaccination was published as a non-peer-reviewed pre-print in medRxiv in September.⁵ According to the report, the most frequent adverse events among the 18-55 age groups were fatigue, headache and myalgia. Fever was reported in 76 (19%) participants, with grade 3 fever reported in 22 (5%) participants. All fevers occurred within 2 days of immunization and resolved within 1 to 2 days. The most frequent adverse events among the group of 65 years or older were headache, fatigue and myalgia. Mild or moderate fevers of grade 1 or 2 were reported in 4% of participants. This finding suggests that the vaccine candidate is less able to cause immunologic reaction in older adults.⁵

However, there were two severe adverse events noted in the report: one hypotension, which was later judged by the investigator not to be vaccine-related but was related to a past history of recurrent hypotension; and one hospitalized overnight with fever but recovered within 12 hours, the fever was later judged by the investigator to be vaccine related. No participant discontinued the study due to an adverse event. Therefore, according to the scientists of the study, “the safety profile is acceptable at any age, given the seriousness of the disease the vaccine can potentially protect against, and the nature of the pandemic, especially in the elderly which is the population most vulnerable to COVID-19.”⁵

A single dose of Ad26.COV2.S elicited strong humoral responses in the vast majority of vaccine recipients. Specific spike protein of SARS-CoV-2 antibody titers (concentration) increased from baseline to Day 29 post vaccination in 99% of the participants in cohort 1a, and 100% of the first participants in cohort 3, with either vaccine dose levels (5x10¹⁰ or 1x10¹¹ viral particles per vaccination).⁵

Ad26.COV2.S also elicited cellular immune response. Spike protein specific CD8+ T cell responses were also identified after the vaccination. On the 15th days after vaccination, 51% of cohort 1a participants (18-55 years old) administered with 5x10¹⁰ viral particles, and 64% of cohort 1a participants administered with 1x10¹⁰ viral particles, showed positive CD8+ T cell response to Spike peptide stimulation. Of participants of age 65 or above, 33% had a detectable vaccine induced CD8+ T cell response for both dose level groups.

The study is still ongoing; on 4th October, J&J announced another interim analysis from it.⁶ The data demonstrates that a single dose of the vaccine candidates induced a strong neutralizing antibody response in nearly all participants aged 18 years and older, and was generally well-tolerated. Immune responses were similar across the age groups studied, including older adults.

Since both dose levels showed similar immunogenicity, the company decided to use lower dose (5x10¹⁰ viral particles per vaccination) for the phase 3 clinical evaluation.

Phase 3
Once the first interim result from the phase 1/2a study was out, a phase 3 trial on the vaccine candidate (NCT04505722) evaluating a single-dose regimen on a much larger scale started in September. The phase 3 trial, also called ENSEMBLE, is expected to enrol a total of 60,000 volunteers across 3 continents: Africa, South and Central America, and the United States.⁷ The phase 3 study in the US experienced a temporary pause once in mid October, but resumed later after about 2 weeks.^8,9

Another phase 3 study with a two-dose regimen (NCT04614948) is yet to be started later this year.10 The trials taking place in the UK will recruit a total of 6000 volunteers and are expected to finish in the first quarter of 2021.¹¹

Comments on the project
According to the UK government, Ad26.COV2.S is the third potential vaccine to enter clinical trials in the UK. The first two are the vaccines from a US biotech company Novavax and from the University of Oxford/ AstraZeneca.¹¹

The whole project of examining the vaccine candidate is highly transparent. Reports and Interim reports were available to the public to get the data from the pre-clinical and clinical trials studies.^3,5,6 The protocol of phase 3 trials is clearly written and is also available online to the public.¹² However, a serious medical event experienced by one study participant in the US, which caused the temporary pause of the phase 3 study, has not been clearly described or explained. Although they obtained consent from the Data Safety and Monitoring Board (DSMB), the US Food and Drug Administration (FDA), and the Institutional Review Boards to resume the study in the US, with no clear cause yet identified, the incident is something that the public may need to be cautious of.⁹

Ad26.COV2.S was developed using the technology platform, AdVac®,* which was developed by Janssen Pharmaceuticals. The platform has been used to design and develop an Ebola vaccine which was later used for 2 million doses and got approval from the European Commission. Based on the safety records for the viral vaccine using the AdVac platform, there should be no safety hazard for using AdVac as the Ad26.COV2.S backbone structure.¹³

This project has obtained a lot of funds to support the studies. The project is sponsored by Johnson and Johnson and funded, in part, by Biomedical Advanced Research and Development Authority (BARDA) under contract HHS0100201700018C.^3,5 BARDA is part of the Office of the Assistant Secretary for Preparedness and Response (ASPR) at the US Department of Health and Human Services. Under the contract, BARDA and Johnson & Johnson together have committed to invest more than $1 billion for the candidate vaccine’s research, development, and clinical testing.² The UK government’s Vaccine Taskforce also jointly fund Johnson & Johnson to test the safety and effectiveness of the vaccine candidate.¹¹

Since its entry into the clinical phases, the vaccine candidate has already been a purchase target of many nations. In early October, Janssen Pharmaceutical Companies signed an Advanced Purchase agreement with the European Commission to supply 200 million doses, and an extra of up to 200 million more doses of Ad26.COV2.S, to European Union Member States, following the approval or authorization from regulators.¹⁴ In early August, Janssen Pharmaceutical Companies have also agreed with the US government to deliver 100 million doses of Ad26.COV2.S for use in the United States following approval or Emergency Use Authorization by the US Food and Drug Administration (FDA). The US government may also purchase an extra 200 million doses under a subsequent agreement.¹⁵

Johnson & Johnson has a goal to supply more than one billion doses globally through the course of 2021, provided the vaccine is safe and effective.^2,15 In order to meet this goal, the company has started to invest to expand its capacity to produce the viral vaccine since March this year.2 Moreover, the company is also collaborating with Aspen Pharmacare, a South African pharmaceutical company, to commercially manufacture its COVID-19 vaccine. In addition to the use of the technology platform, AdVac®* make the production of the vaccine candidate ready to be upscaled rapidly if it is being approved. In fact, using the same platform, two million of the Ebola 2-shot vaccine regimens, Zabdeno® (Ad26.ZEBOV) and Mvabea® (MVA-BN-Filo), were produced in less than one year for the Ebola epidemic in West Africa.^1,13

Introduction to the organizations and companies involved in development of the vaccine
Beth Israel Deaconess Medical Center (BIDMC) is a part of the Beth Israel Lahey Health system. It is a teaching hospital of Harvard Medical School. The Director of the Center for Virology and Vaccine Research at BIDMC is Dan Barouch, M.D., Ph.D. Dr. Barouch's team is well-known for their work on the pathogenesis and immunology of viral infections and the development of vaccine strategies for global infectious diseases.¹

The collaboration between the team led by Dr. Barouch and the Janssen Pharmaceuticals have been in progress much longer than the development of a vaccine for COVID-19. The two sides started collaborating since the development and preclinical work for Zika and HIV vaccine candidates a few years ago.

Janssen Pharmaceutical Companies belongs to Johnson and Johnson (J&J). J&J has been established for more than 130 years. It has the biggest market capital among the diversified medical stock. They focus on the wide areas of medicine: cardiovascular and metabolism, immunology, infectious diseases and vaccines, neuroscience, oncology, and pulmonary hypertension.



*AdVac® is based on a specific type of adenovirus, which has been genetically modified so that it can no longer replicate in humans and cause disease. The AdVac® technology helps to accelerate the development of vaccines. The technology has been used in developing Ebola (which also utilizes its MVA-BN® technology), Zika, RSV and HIV vaccines. The Ebola vaccine has now received approval by the European Commission and has been deployed in some areas in Africa. “Vaccine Technology. Janssen Pharmaceutical website. https://www.janssen.com/infectious-diseases-and-vaccines/vaccine-technology”





References
1. Johnson & Johnson announces collaboration with the Beth Israel Deaconess Medical Center to accelerate COVID-19 vaccine development. Press release from Janssen Pharmaceutical companies. Mar 13, 2020. https://www.janssen.com/johnson-johnson-announces-collaboration-beth-israel-deaconess-medical-center-accelerate-covid-19
2. Johnson & Johnson announces a lead vaccine candidate for COVID-19; Landmark new partnership with U.S. Department of Health & Human Services; and commitment to supply one billion vaccines worldwide for emergency pandemic use. Johnson & Johnson news release, March 30, 2020. jnj.com/johnson-johnson-announces-a-lead-vaccine-candidate-for-covid-19-landmark-new-partnership-with-u-s-department-of-health-human-services-and-commitment-to-supply-one-billion-vaccines-worldwide-for-emergency-pandemic-use
3. N.B. Mercado, R. Zahn, F. Wegmann, et al. Single-shot Ad26 vaccine protects against SARS-CoV-2 in rhesus macaques. Nature, 2020 Oct;586(7830): 583-588.
4. A study of Ad26.COV2.S in adults (COVID-19). NCT04436276. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT04436276
5. J. Sadoff, M. Le Gars, G. Shukarev, et al. Safety and immunogenicity of the Ad26.COV2.S COVID-19 vaccine candidate: interim results of a phase 1/2a, double-blind, randomized, placebo-controlled trial. MedRxiv, September 25, 2020. https://doi.org/10.1101/2020.09.23.20199604
6. Johnson & Johnson Posts Interim Results from Phase 1/2a Clinical Trial of its Janssen COVID-19 Vaccine Candidate. Johnson & Johnson news release, Oct 4, 2020. https://www.jnj.com/johnson-johnson-posts-interim-results-from-phase-1-2a-clinical-trial-of-its-janssen-covid-19-vaccine-candidate
7. A study of Ad26.COV2.S for the prevention of SARS-CoV-2-mediated COVID-19 in adult participants (ENSEMBLE). NCT04505722. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT04505722
8. Johnson & Johnson temporarily pauses all dosing in our Janssen COVID-19 vaccine candidate clinical trials. Janssen Pharmaceuticals’ press release, Oct 13, 2020. https://www.janssen.com/johnson-johnson-temporarily-pauses-all-dosing-our-janssen-covid-19-vaccine-candidate-clinical-trials
9. Johnson & Johnson prepares to resume phase 3 ENSEMBLE trial of its Janssen COVID-19 vaccine candidate in the U.S. Johnson & Johnson news release, Oct 23, 2020. https://www.jnj.com/our-company/johnson-johnson-prepares-to-resume-phase-3-ensemble-trial-of-its-janssen-covid-19-vaccine-candidate-in-the-us
10. A study of Ad26.COV2.S for the prevention of SARS-CoV-2-mediated COVID-19 in adults (ENSEMBLE 2). NCT04614948. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT04614948
11. Janssen to begin COVID-19 vaccine trials in the UK. Gov.UK press release, 16 November 2020. https://www.gov.uk/government/news/janssen-to-begin-covid-19-vaccine-trials-in-the-uk
12. A randomized, double-blind, placebo-controlled phase 3 study to assess the efficacy and safety of Ad26.COV2.S for the prevention of SARS-CoV-2-mediated COVID-19 in adults aged 18 years and older. https://www.jnj.com/coronavirus/covid-19-phase-3-study-clinical-protocol.
13. Vaccine technology. Janssen Pharmaceutical Companies. https://www.janssen.com/infectious-diseases-and-vaccines/vaccine-technology
14. Johnson & Johnson Announces European Commission Approval of Agreement to Supply 200 Million Doses of Janssen’s COVID-19 Vaccine Candidate. Janssen Pharmaceuticals’ news release, Oct 8, 2020. https://www.janssen.com/johnson-johnson-announces-european-commission-approval-agreement-supply-200-million-doses-janssens
15. Johnson & Johnson Announces Agreement with U.S. Government for 100 Million Doses of Investigational COVID-19 VaccineJohnson & Johnson Announces Agreement with U.S. Government for 100 Million Doses of Investigational COVID-19 Vaccine. Janssen Pharmaceuticals’ news release, Aug 05, 2020. https://www.jnj.com/johnson-johnson-announces-agreement-with-u-s-government-for-100-million-doses-of-investigational-covid-19-vaccine

Coronavirus (26) Non-replicating viral vectored vaccine candidates for COVID-19 (part c)

Coronavirus (26) Non-replicating viral vector vaccine candidates for COVID-19 (part c)
Continued from my last blog post.
3. Sputnik V by Gamaleya Research Institute
Sputnik V, formerly known as Gam-COVID-Vac, was developed by the Gamaleya Research Institute in Moscow. It was the world’s first registered vaccine for COVID-19, which was approved by the Ministry of Health of the Russian Federation on 11th August. ¹

The other non-replicating virus vectored vaccine candidates for COVID-19 use only a single recombinant virus as a vector, but Sputnik V uses different recombinant adenoviruses for the first (prime dose) and the second vaccination (booster dose). The two adenovirus vectors, adenovirus type 5 (Ad5) and adenovirus type 26 (Ad26), were inserted with the same whole spike glycoprotein nucleotide sequence to express Spike protein of SARS-CoV-2. The vaccine using Ad26 as viral vector (rAd26-S) was administered for the first shot in vaccination (primary vaccination), and the vaccine using Ad5 as viral vector (rAd5-S) is then administered in the second shot in vaccination (booster). According to the Gamaleya Research Institute, this kind of heterologous vaccination can overcome negative effects of immune response to the vector component.*

Gamaleya Research Institute were already using this heterologous-vector-based approach to develop two vaccines against Ebola, both of which were approved for use by the Ministry of Health of the Russian Federation.^1,2

Phase 1/2
Report on two open, non-randomised phase 1 and 2 studies on Sputnik V at two hospitals in Russia were published in The Lancet in September.³ The trials recruited 76 participants (38 in each study) aged 18 to 60, starting from 18th June this year. One study (NCT04436471)⁴ used frozen formulation, while the other study (NCT04437875)⁵ used lyophilized formulation of the vaccine candidate. Each study had a phase 1 trial that included 18 volunteers receiving intramuscularly one dose of either Sputnik V with Ad26 as viral vector (rAd26-S, 9 participants) or Sputnik V with Ad5 as viral vector (rAd5-S, 9 participants), and a phase 2 trial that included 20 volunteers for heterologous prime-boost vaccination, with rAd26-S given on day 0 and rAd5-S on day 21.³

The results from the studies found that both frozen and lyophilized formulations of Sputnik V were safe and well tolerated. Among the 78 participants, the most common adverse events after vaccination were pain at injection site (44 [58%]), hyperthermia (38 [50%]), headache (32 [42%]), asthenia (21 [28%]), and muscle and joint pain (18 [24%]). Most adverse events were mild. No serious adverse events were detected.

All 78 participants produced specific IgG antibodies** to the receptor binding domain of Spike glycoprotein of the SARS-CoV-2, as measured 21 days after vaccinations. At day 42, the average serum levels of IgG against receptor binding domain of the Spike glycoprotein were higher for the group administered with frozen formulation than the group administered with lyophilized formulation (GMT 14,703 vs GMT 11,143).*** The average levels of neutralising antibodies against the coronavirus were 49.25 for the frozen formulation and 45.95 for the lyophilized formulation. This shows that Sputnik V induces humoral immunity with the frozen formulation triggering a higher level.

Cell-mediated T-cell responses were detected in all participants at day 28, with median cell proliferation of 2.5% CD4+ and 1.3% CD8+ with the frozen formulation, and a median cell proliferation of 1.3% CD4+ and 1.1% CD8+ with the lyophilized formulation. Again, this shows that Sputnik V induces cellular immunity, with the frozen formulation triggering a higher level.

Another open-ended, non-random phase 2 study (NCT04587219)⁶ aiming to investigate the prime-boost vaccination (with rAd26-S given on day 0 and rAd5-S on day 21) using frozen formulations of the vaccine on 110 participants aged 60 or above, has just been started on 22nd October. This study is expected to finish by the end of the year.

Phase 3
The phase 3 trial (NCT04530396) estimated to recruit a total of 40,000 participants started on 7th September.⁷ It is a randomized, double-blind (blinded for both the trial subject and the study physician), placebo controlled, multi-centre clinical trial to examine the efficacy, immunogenicity, and safety of the frozen formulation of the combined vector vaccines (rAd26-S given on day 0 and rAd5-S on day 21) against the SARS-CoV-2-induced coronavirus infection in adults age 18 or above. The study is expected to be completed in May 2021.

The whole project is supported by the Russia Direct Investment Fund. Moreover, the Gamaleya Research Institute has accumulated a lot of experiences in using adenoviruses as vectors to develop vaccines. The scientists of this lab first started to develop vaccines using adenoviruses in the 1980s. Therefore, the research centre should have enough funding and ability to develop and to test the vaccine candidate, and to mass produce the vaccine candidate for the public if it is approved to be used.

However, Sputnik V has sparked controversies among scientists around the world since the Russian government tried to accelerate the registration of this vaccine candidate. Only two months after the start of the early stage of the clinical trials in June, which included just 76 participants, the Ministry of Health of the Russian Federation already issued a registration certificate for the vaccine candidate and approved the use of it in August.⁸ Although the vaccine was to be given to “a small number of citizens from vulnerable groups,” including medical staff and the elderly, the certification was denounced by the scientists as “immature and inappropriate”. This raised considerable concern about the vaccine’s safety and efficacy, especially as the phase 3 trial study which recruits many more volunteers was yet to be launched one month later in September.⁸

The interim report of the phase 3 study, which has just been released on 11th of this month, has sparked another controversy.^9-11 The report announced 92% efficacy, however, it is only the result from 20 total COVID-19 cases in the vaccinated and placebo groups. This is far too few for the claim to be convincing.^10,11 The report was released two days after the announcement from Pfizer and BioNTech on a 90% efficacy of their RNA vaccines against COVID-19. With scant data presented in the release, the rushing of the announcement make it feel like that Russia was merely trying to keep up with their competitors in other countries in the international vaccine race.¹⁰

Moreover, the use of Ad5 as a carrier vector in one of the shots of Sputnik V has also raised concern of increase susceptibility to HIV. Previous experience suggested that non-HIV vaccine trials that use Ad5 as viral vector in areas of high HIV prevalence, such as South Africa, could lead to an increased risk of HIV-1 acquisition in the vaccinated population.¹²

About Gamaleya Research Institute
The Gamaleya Research Institute of Epidemiology and Microbiology in Moscow was founded in 1891 by Nikola Gamaleya as a private laboratory. It has borne the name of Nikolai Gamaleya since 1949. Gamaleya Center is now led by Alexander Gintsburg, Doctor of Biology, Member of the Russian Academy of Sciences.¹ The Gamaleya Research Center is currently developing vaccines against influenza and against Middle East Respiratory Syndrome (MERS) using adenoviral vectors. Both vaccines are in advanced stages of clinical trials.¹



* “When using vector-based vaccines, immune responses are formed not only to the target antigen expressed from the gene inserted to the viral vector. As a result, the best vaccination scheme is heterologous vaccination, when different viral vectors are used to overcome any negative effects of immune response to vector components.” ²
** Detection of specific IgG antibodies to the receptor binding domain of Spike glycoprotein of the SARS-CoV-2 from the participants’ blood indicates the successful triggering of the production of antibodies against SARS-CoV-2 by the vaccine candidates.
***GMT: Geometric Mean Titre is the average antibody titre (concentration) for a group of people. The value is usually useful to evaluate the immune responses.





References
1. Information from the website of Sputnik V vaccine: https://sputnikvaccine.com
2. I.V. Dolzhikova, O.V. Zubkova, and A.I. Tukhvatulin, et al. Safety and immunogenicity of GamEvac-Combi, a heterologous VSV- and Ad5-vectored Ebola vaccine: an open phase I/II trial in healthy adults in Russia. Hum. Vaccin. Immunother., 2017; 13: 613-620.
3. D.Y. Logunov, I.V. Dolzhikova, O.V. Zubkova, et al. Safety and immunogenicity of an rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine in two formulations: two open, non-randomised phase 1/2 studies from Russia. The Lancet, 2020, 395,10255, 887-897.
4. An open study of the safety, tolerability and immunogenicity of the drug "Gam-COVID-Vac" vaccine against COVID-19. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT04436471
5. An open study of the safety, tolerability and immunogenicity of "Gam-COVID-Vac Lyo" vaccine against COVID-19. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT04437875
6. The study of "Gam-COVID-Vac" vaccine against COVID-19 with the participation of volunteers of 60 y.o and older. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT04587219
7. Clinical trial of efficacy, safety, and immunogenicity of Gam-COVID-Vac vaccine against COVID-19 (RESIST). ClinicalTrials.gov. https://www.clinicaltrials.gov/ct2/show/NCT04530396
8.Russia’s approval of a COVID-19 vaccine is less than meets the press release. By Jon Cohen. Science, Aug. 11, 2020. https://www.sciencemag.org/news/2020/08/russia-s-approval-covid-19-vaccine-less-meets-press-release
9. The first interim data analysis of the Sputnik V vaccine against COVID-19 phase III clinical trials in the Russian Federation demonstrated 92% efficacy. Press release from Sputnik V. https://sputnikvaccine.com/newsroom/pressreleases/the-first-interim-data-analysis-of-the-sputnik-v-vaccine-against-covid-19-phase-iii-clinical-trials-/
10. Russia’s claim of a successful COVID-19 vaccine doesn’t pass the ‘smell test,’ critics say. By Jon Cohen. Science, Nov. 11, 2020. https://www.sciencemag.org/news/2020/11/russia-s-claim-successful-covid-19-vaccine-doesn-t-pass-smell-test-critics-say 11. Russia announces positive COVID-vaccine results from controversial trial. By Ewen Callaway. Nature News, 11 November, 2020. https://www.nature.com/articles/d41586-020-03209-0
12. S.P. Buchbinder, M.J. McElrath, C. Dieffenbach, et al. Use of adenovirus type-5 vectored vaccines: a cautionary tale. Lancet, 2020, Oct 31; 396 (10260): E68-E69.

Coronavirus (25) Non-replicating viral vectored vaccine candidates for COVID-19 (part b)

Coronavirus (25) Non-replicating viral vector vaccine candidates for COVID-19 (part b)
Continued from my last blog post.
2. Adenovirus vectored vaccine by CanSinoBio
This vaccine was co-developed by CanSino Biological Inc. and Beijing institute of Biotechnology.¹ It is basically a replication-defective adenovirus (type 5, Ad5) as vector and engineered to contain and express full-length spike glycoprotein of SARS-CoV-2. It is manufactured in liquid form which contains 5x10⁵ virus particles in 0.5ml in a vial. The vaccine candidate has finished its phase 1 and phase 2 trials and is now in the phase 3 trials.

Phase 1
The phase 1 trial started on 16 March this year in Wuhan. The trial was done in an open-labelled, non-randomised manner. The study recruited 108 participants aged 18-60 which were then divided into 3 groups to receive 3 different doses (5x10¹⁰ (n=36), 1x10¹¹ (n=36), 1.5x10¹¹ (n=36) viral particles) via intramuscular injection.

Within 7 days after the vaccination, eighty-seven cases (81%) reported to have at least one adverse reaction. The most common adverse reaction was injection site pain (n=58, 54%). Systemic adverse reactions such as fever (n=50, 46%), fatigue (n=47, 44%), headache (n=42, 39%), and muscle pain (n=18, 17%) were also commonly reported. There was no significant difference in the overall number of adverse reactions across the treatment, and most adverse reactions were mild or moderate in severity. No serious adverse event was noted within 28 days after vaccination. However, a higher proportion of participants reported grade 3 (higher grade of severity) adverse reactions in the highest dose group (1.5×10¹¹ viral particles, 17%) compared with the low-dose (5×10¹⁰ viral particles, 6%) or middle-dose (1×10¹¹ viral particles, 6%) groups.²

The vaccine injection caused significant increase in neutralising antibodies at day 14, and peaked at day 28. Specific T-cell responses to vaccination were found peaked on day 14 instead of day 28.²

Phase 2
Phase 2 clinical trials started on 11th April this year and took place in Wuhan. The trial was done in a randomised, double-blind, and placebo-controlled manner. The study included 508 participants which were than divided to receive either 1x10¹¹ viral particles (n=253), 5x10¹⁰ viral particles (n=129), or a placebo that contained no virus particles (n=126).

The study found that most adverse reactions after vaccine injection were mild or moderate, and mostly resolved within no more than 48 hours. Vaccine recipients had a significantly higher proportion of adverse reactions, within 28 days after vaccination, than those in placebo recipients. Among recipients of either dose of the Ad5-vectored COVID-19 vaccines, almost all of the most severe adverse reactions were reported from the participants who received 1×10¹¹ viral particles, with only one was reported from a participant received 5×10¹⁰ viral particles.

Similar to the results of the phase 1 study, the antibody responses were detected on day 14, and peaked on day 28 after vaccination in recipients who randomly received the vaccine candidate, but not detected on the control group. Both vaccine recipient groups showed comparable specific immune responses to the spike glycoprotein at day 28, with no significant difference between the two groups. However, in contrast to expectations, the vaccine at 5×10¹⁰ viral particles had a comparable immunogenicity to the vaccine at 1×10¹¹ viral particles.

The scientists involved in the study are concerned that the pre-existing adenovirus vector (type 5) may affect the efficiency of the vaccine candidate. In the phase 2 study, they did experiment to examine this issue. The study found that the immunity against Ad5, which indicates the pre-existing Ad5, and age, could affect the safety of the vaccine candidate and its ability to induce immune responses: fever, which reflects the immune response, was associated with younger participants and a lower level of immunity to Ad5 virus. Among the 21 participants who experienced a higher severity of fever, nineteen (90%) had no pre-existing immunity to Ad5. On the other hand, the immune responses to the vaccine candidate were significantly lower with increasing age and high pre-existing Ad5 levels. The study thus assumed that one injection of the vaccine might not be enough to induce a specific immune response for people aged 55 and older.

The results from the phase 2 study showed that vaccination of the Ad5-vectored COVID-19 vaccine at a dose of 5x10¹⁰ viral particles has a better safety profile than, and comparable immunogenicity to, the vaccine with dose of 1 × 10¹¹ viral particles. The report of the phase 2 study thus suggests testing of the Ad5-vectored COVID-19 vaccine at 5×10¹⁰ viral particles in a phase 3 effectiveness trial in healthy adults.

Phase 3
The phase 3 clinical trials (NCT04526990) is a randomized, double-blind, placebo-controlled trial aiming to recruit 40,000 participants, age 18 or above, in multiple centres.4 According to the data from ClinicalTrials.gov, the countries involved in the study include Pakistan. Moreover, CanSino Biotech also collaborated with NPO Petrovax, a Russian biotech company, to conduct a randomized, double-blind phase 3 study that aimed to recruit 500 participants age 18 to 85 years (NCT04540419).⁵ They expect the primary study will be completed on 30th November.

So far, the clinical trials for this vaccine candidate have been running smoothly. However, it was already given approval for military use in China at the end of June, before the phase 3 trials started.⁶ That rush to use the vaccine before more convincing safety and efficacy data from a larger population raises concerns that the clinical studies may not have been done properly enough to examine the safety and efficacy of the vaccine candidate.

Moreover, the using of Ad5 as a carrier vector may also increase the patient’s susceptibility to HIV. Previous experience suggested that non-HIV vaccine trials that use Ad5 as viral vector in areas where HIV is prevalent, such as South Africa, could lead to an increased risk of HIV-1 acquisition in the vaccinated population.⁷

About CanSinoBio康希樂生物
CanSinoBIO, SHSE: 688185, HKEX:06185, was incorporated in 2009 in Tianjin, China. It’s focus is to produce and commercialize vaccine for China and global market. It possesses four integrated platform technologies including adenovirus-based vectors, conjugation, protein design and recombination and formulation. Today, the company has more than 600 employees. It has established a pipeline of 16 vaccine candidate covering 13 infectious diseases in product line. Their vaccine for Ebola virus (Ad5-EBOV) received approval in 2017.⁸





References
1. China’s progress in developing COVID-19 vaccines could surprise the world, GlobalData says. 12 July, 2020. News Medical. https://www.news-medical.net/news/20200721/Chinae28099s-progress-in-developing-COVID-19-vaccines-could-surprise-the-world-GlobalData-says.aspx
2. F.C. Zhu, Y.H. Li, and X.H. Guan, et al. Safety, tolerability, and immunogenicity of a recombinant adenovirus type-5 vectored COVID-19 vaccine: a dose-escalation, open-label, non-randomised, first-in-human trial. The Lancet, 2020, 395, 1845-1854.
3. F.C. Zhu, X.H. Guan, and Y.H. Li, et al. Immunogenicity and safety of a recombinant adenovirus type-5-vectored COVID-19 vaccine in healthy adults aged 18 years or older: a randomised, double-blind, placebo-controlled, phase 2 trial. The Lancet, 2020, 396, 479-488.
4. Phase III trial of a COVID-19 vaccine of Adenovirus vector in adults 18 years old and above. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT04526990
5. Clinical trial of recombinant novel coronavirus vaccine (adenovirus type 5 vector) against COVID-19. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/study/NCT04540419
6. CanSino's COVID-19 vaccine candidate approved for military use in China. Reuters, Health news. June 29, 2020. https://uk.reuters.com/article/us-health-coronavirus-china-vaccine/cansinos-covid-19-vaccine-candidate-approved-for-military-use-in-china-idUKKBN2400DZ
7. S.P. Buchbinder, M.J. McElrath, C. Dieffenbach, et al. Use of adenovirus type-5 vectored vaccines: a cautionary tale. The Lancet, 2020, Oct 31; 396 (10260): E68-E69.
8.CanSinoBIO Overview. http://www.cansinotech.com/html/1//173/174/index.html

Coronavirus (24) Non-replicating viral vectored vaccine candidates for COVID-19 (part a)

Coronavirus (24) Non-replicating viral vectored vaccine candidates for COVID-19 (part a)
WHO updated their list of vaccines for COVID-19 on 29th October.¹ There are now 45 vaccine candidates in the clinical trials phases. Adding three more countries, Israel, Kazakhstan and Kosovo, at the forefront of the race to develop COVID-19 vaccines.

In this and the coming few blog posts, I am going to introduce you to non-replicating viral vectored vaccine candidates for COVID-19 which have already entered phase 3 of clinical trials.

A vaccine with a viral vector platform is basically a genetically-modified virus with a specifically chosen gene from a target pathogen inserted into it by recombinant technology. The virus serves as a vector to deliver the inserted gene into human cells. Once injected via vaccination, the virus vector enters into human cells and the inserted gene starts to express itself as a protein, which acts as an antigen, triggering the immune response to produce antibodies against that antigen. According to the data from WHO, all of the viral vectored vaccine candidates for COVID-19 are inserted with nucleotide sequences that express the Spike glycoprotein (S) of SARS-CoV-2.* Therefore, these viral vectored vaccine candidates for COVID-19 are expected to trigger the production of antibodies against the surface Spike protein of the coronavirus. These antibodies block the interaction between the coronavirus and human cells, thus inhibiting the viral infection next time it invades.

The virus which acts as a vector in the non-replicating virus vectored vaccine is modified so that the gene(s) that cause infection and the gene(s) responsible for replication have been removed. Therefore the virus vector of the vaccine will not cause disease and will not give rise to a copy of itself once the vaccine is injected. In other words, once non-replicating vectored vaccines enter cells, they produce the vaccine antigen expressed from the inserted gene, but no new virus particles are formed. This means that the amount of the virus particles injected into the body via vaccination is under control and thus cause no underlying safety hazard.

One advantage of these viral vector-based vaccines is that a single dose is usually sufficient for protection.² However, most of the COVID-19 vaccines using non-replicating virus as vector require two doses.

Vaccines with non-replicating viral vector as a platform started being developed only in recent decades. The most commonly used virus vector is human adenovirus. The use of human adenoviruses as vectors is safe because these viruses, which cause the common cold, are not novel and have been around for thousands of years.

According to the latest information provided by WHO,¹ there are now 9 non-replicating viral vaccines in the clinical trials. Four are in phase 3, and five in early phase trials.

Non-replicating viral vector vaccines in clinical trials:
1. AZD1222 by Vaccitech, Jenner Institute in Oxford, and AstraZeneca
The development of the vaccine AZD1222 is a good example of collaboration between a university and industry. The vaccine candidate was co-invented by the Jenner Institute in University of Oxford and its spin-out company called Vaccitech. The University of Oxford later partnered with AstraZeneca in late April to do further investigation on the vaccine candidate. Phase 1 and phase 2 (NCT04324606) was finished in the summer and the phase 3 started in late August.

AZD1222 was formerly known as ChAdOx1 nCoV-19. It is made from an adenovirus called ChAdOx1, a weakened version of a common cold virus that causes infections in chimpanzees. ChAdOx1 was developed at the Jenner Institute in Oxford. It has been genetically changed so that it is impossible for it to grow in humans. The adenovirus carries DNA for the spike antigen of SARS-CoV-2.

Phase 1 and 2 studies
The result of the phase 1 and 2 trials of the vaccine candidate was published in August.^3,4 The early phase trial was a single-blind, randomized trial using the vaccine candidate and a meningococcal conjugate vaccine (MenACWY) as control. The trial was done in 5 trial sites in the UK with 1077 healthy adults between 18 and 55 years old and with no history of laboratory confirmed SARS-CoV-2 infection. Of these, 543 were randomly assigned the vaccine and the other 534 assigned as the control to receive a single intramuscular injection.

The study found that transient local and systemic reactions, such as injection site pain, feeling feverish, chills, fatigue, muscle ache, mild to moderate headache, and malaise, were more common in the ChAdOx1 nCoV-19 group than in the control group. However, the symptoms were comparable to previous trials and other adenoviral vector vaccines. The symptoms could be reduced with the use of paracetamol before administering the vaccine. There were no serious adverse events related to the vaccine, showing it has an acceptable safety profile.

The vaccine injection induced both humoral** and cellular*** immune responses. In the group administered with ChAdOx1 nCoV-19, all participants showed spike-specific T-cell responses which peaked by day 14 and maintained for two months after injection. A single dose of the vaccine resulted in a four-fold increase in antibodies to the SARS-CoV-2 virus spike protein in 95% of participants, 28 days after injection. Neutralising activity against SARS-CoV-2, assessed by the MNA80 assay#, was seen in 91% of participants one month after vaccination and in 100% of participants who received a second dose.⁴ There was strongest immune response in participants who received two doses of the vaccine, indicating that this might be a good strategy for vaccination.

Phase 3 studies
The vaccine was the first COVID-19 vaccine to begin phase 3 studies, in the UK, Brazil, South Africa, the US, and Europe. However, these trials did not go smoothly all the way. The global trials of the vaccine were once paused on 6th September, after a person participating in the UK trial experienced an adverse reaction.⁵ The clinical trials in the UK then resumed a few days later and the FDA authorized the restart of the trial in the US, more than one month later, on 23rd October. Oxford University and AstraZeneca were criticised on their lack of transparency, as some scientists claimed that key details of the events involved have not been released and the decision to restart the trials was too quick.^6,7

Actually, according to an article in ClinicalTrialsArena, the trials on the vaccine candidates were paused for two incidences, both occurring in UK-based volunteers.⁷ The first temporary pause happened in July after a participant experienced multiple sclerosis (MS), and the second pause was the one on 6 September, when a participant experienced transverse myelitis. Transverse myelitis and MS are neurological conditions.

AstraZeneca already has commitments to supply more than two billion doses of the vaccine to the UK, the US, Europe’s Inclusive Vaccines Alliance, the Coalition for Epidemic Preparedness, Gavi the Vaccine Alliance and Serum Institute of India.⁴

About Jenner Institute in University of Oxford
The Jenner Institute was founded in November 2005 in partnership with the Institute for Animal Health. It is based within the Nuffield Department of Medicine, University of Oxford. The Institute supports senior vaccine scientists, known as Jenner Investigators, within many other departments across the University of Oxford, as well as externally within The Pirbright Institute and the Animal and Plant Health Agency, to design and develope vaccines. ⁸

The Jenner Institute is supported by the Jenner Vaccine Foundation, a UK registered charity and is advised by the Jenner Institute Scientific Advisory Board.⁸

About Vaccitech
Vaccitech is a clinical stage T cell immunotherapy and vaccine company developing products to treat and prevent infectious disease and cancer. The company’s proprietary heterologous prime-boost platform comprises Chimpanzee Adenovirus Oxford (ChAdOx) and Modified Vaccinia Ankara (MVA), two non-replicating viral vectors which safely mimic viral infection in human cells and elicit high magnitude, durable, targeted CD8+ and CD4+ T cell responses and antibodies to clear foreign pathogens and tumours.⁹

Vaccitech is backed by leading investment institutions, including GV (formerly Google Ventures), Sequoia Capital China, Liontrust (formerly Neptune), Korea Investment Partners and Oxford Sciences Innovation.⁹

About AstraZeneca
AstraZeneca is a British–Swedish multinational pharmaceutical and biopharmaceutical company based in Cambridge. The company was founded in 1999 through the merger of the Swedish Astra AB and the British Zeneca Group. Now it operates in over 100 countries. The company focuses on primarily the treatment of diseases in three therapy areas - oncology, cardiovascular, renal & metabolism, and respiratory & immunology.¹⁰



*The Spike protein is found on the surface of SARS-CoV-2 and is the first critical component which helps the coronavirus to invade human cells. It is responsible for binding to the ACE2 receptor on human cell, leading to the entry of the coronavirus into the cell and causing infection. **Humoral Immune response protects extracellular spaces of the body from bacterial infections. Antibodies produced by B cells cause the destruction of extracellular microorganisms and prevent the spread of intracellular infections. (Immunobiology: The Immune System in Health and Disease. 5th edition. Chapter 9, The Humoral Immune Response. https://www.ncbi.nlm.nih.gov/books/NBK10752/) ***Cellular Immune response is a protective immune process that involves the activation of phagocytes, antigen-sensitized cytotoxic T cells and the release of cytokines and chemokines in response to antigen. (Definition from Nature research. https://www.nature.com/subjects/cellular-immunity) # MNA80 assay (microneutralization assay) is used to measure neutralizing antibody concentration.





References
1. Draft landscape of COVID-19 candidate vaccines. World Health Orgainzation. 29 October, 2020. https://www.who.int/publications/m/item/draft-landscape-of-covid-19-candidate-vaccines
2. Debby van Riel and Emmie de Wit. Next generation vaccines platform for COVID-19. Nature Materials, 2020, vol. 19, 810–820.
3. P.M. Folegatti, K.J. Ewer, and P.K. Aley, et al. Safety and immunogenicity of the ChAdOx1 nCoV-19 vaccine against SARS-CoV-2: a preliminary report of a phase 1/2, single-blind, randomised controlled trial. The Lancet, 2020, 396, p467-478.
4. COVID-19 vaccine AZD1222 showed robust immune responses in all participants in Phase I/II trial. AstraZeneca Media, 20 July, 2020. https://www.astrazeneca.com/media-centre/press-releases/2020/covid-19-vaccine-azd1222-showed-robust-immune-responses-in-all-participants-in-phase-i-ii-trial.html
5. Statement on AstraZeneca Oxford SARS-CoV-2 vaccine, AZD1222, COVID-19 vaccine trials temporary pause. AstraZeneca Media, 9 September, 2020. https://www.astrazeneca.com/media-centre/press-releases/2020/statement-on-astrazeneca-oxford-sars-cov-2-vaccine-azd1222-covid-19-vaccine-trials-temporary-pause.html
6. Scientists relieved as coronavirus vaccine trial restarts — but question lack of transparency. Nature news, updated on 15 September, 2020. https://www.nature.com/articles/d41586-020-02633-6
7. AstraZeneca’s quick Covid-19 vaccine trial restart splits experts. ClinicalTrials comment, Global Data Healthcare, last updated October 12th, 2020. https://www.clinicaltrialsarena.com/comment/azd1222-covid-vaccine-trials-astrazeneca/
8. https://www.jenner.ac.uk/about
9. https://www.vaccitech.co.uk/about/
10. https://www.astrazeneca.com