13 November,2021 08:37 AM IST | Mumbai | Vinod Kumar Menon
A health worker administers a dose of Covaxin at Sir JJ Hospital. The vaccine recently got WHO approval for emergency use. File pic
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The much-awaited data of the phase III trial of Bharat Biotech's Covaxin has finally been released in international medical journal The Lancet, making it the first indigenous vaccine to have published the efficacy in public domain. But, is something missing from the report? Yes, says a Mumbai-based health expert.
The paper published in The Lancet confirms the efficacy analysis of phase III trials, through evaluation of 25,800 volunteers, of whom 130 were symptomatic patients with 24 in the vaccine group and the remaining 106 in the placebo group, that demonstrated Covaxin to be effective against COVID-19 with an efficacy of 65.2 per cent against the Delta variant and 77.8 per cent against symptomatic COVID-19. The analysis further stated that Covaxin is 93.4 per cent effective against severe symptomatic COVID-19.
Similarly, the vaccine is said to have an efficacy of 63.6 per cent against asymptomatic COVID-19 and 70.8 per cent against all variants of the virus.
The safety analysis showed the adverse events reported were similar to placebo, with 12 per cent of subjects experiencing commonly known side-effects and less than 0.5 per cent experiencing serious adverse events.
However, a Mumbai-based health expert raised his concern about the missing crucial T-lymphocytes in calculating the efficacy of Covaxin in this report.
mid-day had, in its July 5 article titled 'Can you trust Covaxin', stated the importance of the third phase trial data to establish efficacy of vaccines.
Dr Wiqar Shaikh, professor of medicine, Grant Medical College and Sir JJ Group of Hospitals, while expressing satisfaction on WHO approval to Covaxin for emergency use, said that the number of subjects in the trial was small for a major vaccine trial.
Dr Shaikh said the efficacy of Covaxin has been calculated on the basis of neutralising antibodies and questioned if this reveals true efficacy. In any viral infection, neutralising antibodies have a limited role to play and the only method used by the body to eliminate virus infected cells is T-lymphocytes.
He concluded that long-term studies of Covaxin are needed, particularly with data on T-lymphocytes, to establish Covaxin as an efficacious, indigenous vaccine.
In response to a query raised by Dr Shaikh about missing T-lymphocytes in calculating efficacy of Covaxin, Bharat Biotech said, "We agree with the point indicating the importance of T-cell response in viral vaccines. Apart from neutralisation antibody titers, we have also done extensive studies to evaluate cell mediated responses in our various clinical trials with Covaxin. Please refer to Phase I and Phase II publications, wherein IFNg secreting T-cell responses, polyfunctional T-cell responses by measuring various cytokines and T-cell memory response were reported. For Phase III, being an efficacy trial, we focused mainly on disease-related end points and measured the efficacy in terms of preventing symptomatic and severe COVID-19."
Countering this, Dr Shaikh said, "As per immunology textbooks, vaccine efficacy cannot be measured through neutralising antibodies alone but should include T-lymphocytes studies. It is still unclear as to why such a crucial part of immunological analysis was missed out in phase III under the ambit of tagging it as an efficacy trial."
However, he lauded the efforts of Bharat Biotech for sharing their data and research studies in public domain, which indicates the transparency at their end, especially at a time, when other vaccine manufacturers have not shared such data on T-cells, which is crucial for not only for gaining public confidence, but also for empowering further research and development in this area.
Dr Ketan Vagholkar, professor of surgery at DY Patil Medical College, said, "It is reassuring and is a reason to be proud that our indigenously produced Covaxin has gained WHO approval. It is an inactivated viral vaccine. Phase III trial results have been published in one of the internationally acclaimed journals. It has excellent protective efficacy against the Delta variants and has negligible side effects, thereby rendering it as a safe option. Bharat Biotech has maintained a high level of transparency as compared to other vaccine producers."
Dr Santosh Bansode, Head of Department, Emergency Medicine, Wockhardt Hospital, said, "After a long wait, Covaxin got approval for emergency use from WHO. We must note that Bharat Biotech followed all protocols and published all trial data."
Dr Krishna Ella, CMD of Bharat Biotech, said, "The peer-review of Covaxin phase III clinical trial data in The Lancet, an authoritative voice in global medicine, validates our commitment to data transparency and meeting the stringent peer-review standards of world leading medical journals."
Dr Balram Bhargava, director-general of Indian Council of Medical Research (ICMR), said, "I am delighted to see that the phase III efficacy data [of Covaxin] has been published in The Lancet, one of the most reputed journals worldwide. This itself speaks highly about the strong position of Covaxin amongst other global front-runners."
77.8
Percentage of Covaxin efficacy against COVID
