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Covaxin shows only 50% efficacy against symptomatic COVID-19: Lancet Study

The latest Covaxin data may dent its appeal at a time when Bharat Biotech is ramping up production while studies show that most vaccines have reduced efficacy against the Delta variant.

A new study published in the Lancet Infectious Diseases journal said that India-made vaccine two doses of Covaxin are 50 per cent effective against symptomatic Covid-19, opening up a host of questions about the coronavirus vaccine, which has been driving the vaccination coverage in the country. For the study, a total of 2,714 symptomatic hospital workers at the All India Institute of Medical Sciences (AIIMS), who were primarily offered Covaxin were assessed, from April 15–May 15.

The results of the interim study showed that two doses of the vaccine manufactured by Bharat Biotech Covaxin, also known as BBV152, had 77.8 per cent efficacy against symptomatic disease and present no serious safety concerns. Researchers noted that the Delta variant was the dominant strain in India during the study period, accounting for approximately 80 per cent of all confirmed Covid-19 cases.

The researchers, including doctors Manish Soneja, Adil Rashid Khan, Devashish Desai, Ankit Mittal and others, said that they received no funding for the study and protocol for it was approved by AIIMS ethics committee. Researchers evaluated the effectiveness of the vaccine against symptomatic RT-PCR confirmed SARS-CoV-2 infection. The study found that the vaccine effectiveness against symptomatic Covid-19 after two doses of Covaxin with the second dose administered 14 or more days before undergoing RT-PCR testing was 50 per cent. The researchers also added that effectiveness remained stable over the seven-week follow up period.

“The vaccine effectiveness estimated in our study is lower than the efficacy announced after completion of the phase 3 trial, despite a similar testing strategy being used (SARS-CoV-2 RT-PCR testing for participants with symptoms suggestive of Covid-19 determined through weekly telephone follow-up),” the researchers noted in the study.