Updated: February 3, 2021 9:05:37 am
An interim analysis of data from the phase 3 trial of the Covid-19 vaccine from Russia — Gam-COVID-Vac, or Sputnik V — suggests that a two-dose regimen offers 91.6% efficacy against symptomatic Covid-19. This is comparable with the efficacy of high-profile vaccines cleared for emergency use in various countries, such as those from Pfizer (95%), Moderna (94.1%) and Oxford-AstraZeneca (up to 90% under a certain regimen).
The preliminary findings are published in The Lancet. The validation in a peer-reviewed journal comes after the vaccine had faced criticism from a section of the scientific community over lack of transparency and the haste at which it had been approved (it was the first vaccine approved for public use anywhere in the world).
The Russian vaccine is being produced in India on a large scale. India has already started vaccinating high-priority groups with Covaxin (Bharat Biotech) and Covishield (Serum Institute of India’s version of the Oxford-AstraZeneca vaccine).
What is the Russian vaccine?
Gam-COVID-Vac is manufactured by the Gamaleya Institute under Russia’s health ministry. It is a two-part vaccine that includes two adenovirus vectors — which carry weakened viral components so that they cannot replicate in the human body. In this case, the vectors have been modified to express the SARS-CoV-2 spike protein.
Sputnik V is already registered in 16 countries; 12 countries will start vaccination In the first week of February this week: Bolivia, Kazakhstan, Turkmenistan, Palestine, UAE, Paraguay, Hungary, Armenia, Algeria, Bosnian Serb Republic, Venezuela and Iran.
Where does the vaccine figure in India?
Hyderabad-based drugmaker Hetero Drugs, through its biologics arm Hetero Biopharma, will be producing “over” 100 million doses of Sputnik V starting this year. The vaccines produced in India may also be used to fulfil demand from other countries.
Sputnik V is undergoing phase 3 trials in India, conducted by Dr Reddy’s Laboratories, also headquartered in Hyderabad. Trials in India are doing well, said Kirill Dmitriev, CEO of the Russian Direct Investment Fund.
What were the trials whose results have been published?
The published results are an analysis of data from nearly 20,000 trial participants, three-quarters of whom received the vaccine and one quarter received a placebo. The trial was conducted across 25 hospitals and polyclinics in Moscow.
Participants were given one initial dose (a vector called rAd26-S), followed days later by a booster dose (another vector, called rAd5-S 21). The authors suggested that using a different adenovirus vector for the booster vaccination may help create a more powerful immune response (compared with using the same vector twice), as it minimises the risk of the immune system developing resistance to the initial vector.
Between September 7 and November 24, 2020, a total of 21,977 adults were randomly assigned to receive the vaccine (16,501) or placebo (5,476). Out of these, 14,964 participants in the vaccine group and 4,902 in the placebo group received two doses of the vaccine or placebo and were included in the primary interim efficacy analysis.
PCR tests were done at screening and at dose 2 (21 days). A further PCR test was done if participants reported symptoms of respiratory infection. Efficacy of the vaccine was calculated on the basis of the proportion of participants with PCR-confirmed Covid-19.
The trial is ongoing and aims to include a total of 40,000 participants. In the published study, the liquid form of the vaccine was used, which requires storage at -18°C. Storage at 2-8°C has also been approved.
What were the findings?
From 21 days after receiving the first dose (the day of dose 2), 16 cases of symptomatic Covid-19 were confirmed in the vaccine group and 62 cases in the placebo group – equivalent to an efficacy of 91.6%.
The vaccine induced a robust antibody response and T-cell immune response, the authors wrote, based on data from 342 and 44 participants, respectively. Six of the 342 participants did not mount an immune response following vaccination, possibly due to older age or individual characteristics.
Serious adverse events (those requiring hospital admission) were rare in both the placebo (0.4%) and vaccine (0.2%) groups and none of these were considered associated with vaccination, the paper said. Four deaths were reported in the trial, none of which were considered related to the vaccine. Most reported adverse events were mild, including flu-like symptoms, pain at injection site and weakness or low energy.
Although the study was not designed to assess the efficacy of a single-dose regimen, the authors said the findings hint to the early onset of a partially protective effect 16-18 days after a single-dose immunisation. The research team recently received approval to investigate the effectiveness of a single-dose regimen of the vaccine.
What are the limitations of these findings?
The authors note that because Covid-19 cases were detected only when participants self-reported symptoms (followed by a PCR test), the efficacy analysis only includes symptomatic cases of Covid-19. They said further research is needed to understand the efficacy of the vaccine on asymptomatic Covid-19, and transmission. Further, median follow-up was 48 days from the first dose, so the study cannot assess the full duration of protection.
Again, most participants in the trial were white. Further research will be needed to confirm the results in a more diverse group of participants, the authors acknowledged.
Although the study enrolled participants with comorbidities, not all risk groups are represented. The authors report a need for further research to investigate the vaccine in adolescents and children, as well as pregnant women. (The trial included 2,144 participants older than 60 years, and vaccine efficacy was 91.8% in this group.)
Why was the vaccine once criticised?
Sputnik V cleared regulatory approvals in August. This was in record time, less than two months after it had got into human trials. This had raised concerns over its safety and effectiveness.
In a comment in The Lancet, Professor Ian Jones, University of Reading, and Professor Polly Roy, London School of Hygiene & Tropical Medicine, UK (who were not involved in the study), have written: “The development of the Sputnik V vaccine has been criticised for unseemly haste, corner cutting, and an absence of transparency. But the outcome reported here is clear and the scientific principle of vaccination is demonstrated, which means another vaccine can now join the fight to reduce the incidence of Covid-19.”
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