Covaxin shows 50 per cent effectiveness against symptomatic Covid in real-world assessment: Lancet study

The results of an interim study recently published in The Lancet shows that two doses of Covaxin had 77.8 per cent efficacy against symptomatic disease and present no serious safety concerns

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New Delhi, November 24

Two doses of Covaxin are 50 per cent effective against symptomatic Covid, according to the first real-world assessment of India's indigenous coronavirus vaccine published in The Lancet Infectious Diseases journal.

The results of an interim study recently published in The Lancet showed that two doses of Covaxin, also known as BBV152, had 77.8 per cent efficacy against symptomatic disease and present no serious safety concerns.

The latest study assessed 2,714 hospital workers at the All India Institute of Medical Sciences (AIIMS) in Delhi, from April 15–May 15, who were symptomatic and underwent RT-PCR test for Covid detection.

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 cases.

Covaxin, developed by Hyderabad-based Bharat Biotech in collaboration with the National Institute of Virology, Indian Council of Medical Research (NIV-ICMR), Pune, is an inactivated whole virus vaccine administered in a two-dose regimen, 28 days apart.

In January this year, Covaxin was approved for emergency use in India for people aged 18 and above. The World Health Organisation (WHO) added the vaccine to its list of approved emergency use Covid vaccines earlier this month.

The latest study was conducted during India's second Covid surge and in healthcare workers who were primarily offered Covaxin.

"Our study offers a more complete picture of how BBV152 (Covaxin) performs in the field and should be considered in the context of Covid surge conditions in India, combined with the possible immune evasive potential of the Delta variant," said Manish Soneja, Additional Professor of Medicine at AIIMS, New Delhi.

"Our findings add to the growing body of evidence that rapid vaccine rollout programmes remain the most promising path to pandemic control while public health policies must continue to include additional protective measures, such as mask-wearing and social distancing," Soneja said in a statement.

The Covid vaccination centre at AIIMS, New Delhi, exclusively offered Covaxin beginning January 16 this year to all of its 23,000 employees.

Researchers evaluated the effectiveness of the vaccine against symptomatic RT-PCR confirmed SARS-CoV-2 infection.

Of the 2,714 employees in the study population, 1,617 people tested positive for SARS-CoV-2, the virus that causes Covid, and 1,097 tested negative.

Positive cases were matched to negative RT-PCR tests (controls).

The odds of vaccination with Covaxin were compared between cases and controls and adjusted for occupational exposure to Covid, previous SARS-CoV-2 infection, and infection dates.

The study found that the vaccine effectiveness against symptomatic Covid after two doses of Covaxin with the second dose administered 14 or more days before undergoing RT-PCR testing was 50 per cent.

The effectiveness of two vaccine doses remained stable over the seven-week follow-up period, the researchers said.

The adjusted vaccine effectiveness of the first dose, estimated after seven and 21 days, was low, which is consistent with the performance of other preventives against the Delta variant, they said. PTI