Health experts say the study has put the indigenous vaccine among global ones, but say need long-term studies
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Amid the debate over the efficacy of booster dose against new variants of SARS-CoV-2, the virus that causes Covid-19, a recent study published in the journal Nature Scientific Report stated that Covaxin is equally effective as 20 other global vaccines. Health experts, however, remained cautious and called for longer studies on preventing occurrence of autoimmune diseases in people with rheumatoid markers affecting heart, kidney, brain, blood and liver as a result of frequent booster doses.
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Vaccine efficacy
“Covaxin is an ancestral whole-virion inactivated SARS-CoV-2 vaccine that is adsorbed onto alum adjuvant to improve its immunogenicity. In 2020, the 6-µg dose of Covaxin was selected for assessment in a phase-3 efficacy trial in which it had demonstrated an overall efficacy of 77.8 per cent against any Covid-19 and 65.2 per cent against the Delta variant. A recently published Phase-2 double-blind study in a peer-reviewed medical journal that assessed the persistence of neutralising antibodies up to 6 months after a two or three‑doses of Covaxin in a randomised controlled trial. The study has reported persistence of humoral and cell mediated immunity up to 12 months. Administration of a third dose increased neutralisation titers against both ancestral and variant strains, namely Alpha, Beta, Delta, Delta Plus and Omicron, with persistent T-cell immunity. Thus, seroconversion rate remained high in boosted recipients compared to non‑boosted individuals, even after 6 months,” said Dr Subhash Hira, professor of Global Health at University of Washington-Seattle and a member of several Covid-vaccine panels at WHO-Geneva.
He added, “However, some studies have raised concerns about excessive use of booster vaccines since they also cause production of auto-antibodies that lead to cardiomyopathies, brain clouding, and kidney-liver damages, in people who are predisposed to autoimmune diseases with rheumatoid markers.”
“After analysing this report, it is clear that vaccines definitely help to protect against Covid-19 infection. So, we must encourage all people to take vaccines. Booster dose is also important to get protection against new variants of concern,” said Dr Santosh Bansode, head of the department, Emergency Medicine, Wockhardt hospitals.
Other vaccines
Dr Wiqar Shaikh, professor of Medicine, Grant Medical College and Sir JJ Group of Hospitals, said that he has noted the recent study on persistence of immunity and impact of third dose of Covaxin.
Dr Shaikh quoted a study published in the New England Journal of Medicine on March 31 from the UK Health Security Agency and other leading research institutions, which studied both the Pfizer and AstraZeneca vaccines. The study concluded that vaccine effectiveness decreased from 85 per cent to 58 per cent within 14 to 73 days and to 51 per cent after 201 days. The study also concluded that 2 doses of the vaccines were associated with high short-term protection but their protection waned considerably after 6 months.
He also cited a study published in the journal medRxiv on March 18 from Qatar University, which studied the Moderna and Pfizer vaccines and concluded that within 23 weeks of administering a double dose of the vaccine, antibody levels were diminished 2 to 6-fold.
Dr Shaikh referred to yet another study, published in the Lancet on March 5 from the WHO department of immunizations and the Johns Hopkins University, USA, which was a systematic review of all studies and data published on COVID vaccines. The study concluded that vaccine efficacy and effectiveness decreased by 20 per cent to 30 per cent within 6 months, which was caused by waning immunity.
He added that the accepted norm worldwide Is that boosters have to be given to protect the population. “However, there is no clarity on the no. of booster doses required. Besides, there has been a repeated demand everywhere that separate vaccines will need to be given for Covid-19 variants,” he said.
Maker Speak
In a media statement, M/s Bharat Biotech stated that the study was conducted in 184 subjects who were evaluated for safety, neutralising antibody responses against variants of concern, binding antibodies against spike protein, RBD, N proteins, and for memory T and B cell responses to demonstrate cell mediated immunity.
Dr Krishna Ella, chairman and MD, Bharat Biotech, said, “Our team has now demonstrated that Covaxin is a multi-epitope vaccine with antibodies against spike, RBD and N proteins. Post booster dose, it has proven neutralising antibody responses against variants of concern and long-term protection through memory T and B cell responses. We have now achieved our goal of developing a safe and efficacious vaccine with long term protection against a spectrum of variants.”
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