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