Wednesday, 16 December 2020

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.

Friday, 11 December 2020

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


Sunday, 6 December 2020

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/

Monday, 30 November 2020

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.

Tuesday, 24 November 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.12



#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

Wednesday, 18 November 2020

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