Covaxin, a vaccine developed by the Indian government’s medical research agency in collaboration with Bharat Biotech International Ltd, was found to have a 77.8% efficacy rate against symptomatic COVID-19, in a study published in The Lancet.

The Lancet said in a statement that Covaxin, which uses traditional, inactivated-virus technology, “induces a robust antibody response” two weeks after two doses are given. A randomised trial involving 24,419 participants aged 18 to 97 years in India between November 2020 and May 2021 found no severe vaccine-related deaths or adverse events, according to the medical journal.

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The interim study, which was funded by Bharat Biotech and the Indian Council of Medical Research and co-authored by officials from both organisations, is consistent with the company’s previous efficacy and safety announcements and could help settle the debate over the shot’s early approval in India in January.

The vaccine had not yet passed final-stage trials at the time, causing widespread scepticism in the early weeks of the immunisation campaign. Over 100 million doses of Covaxin have been distributed across India since then, and the World Health Organization recently added the vaccine to its list of Covid vaccines approved for emergency use. 

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Despite this, the WHO’s independent technical body studying the vaccine repeatedly requested more information from the company, delaying its inclusion on the body’s pre-qualified list and frustrating Prime Minister Narendra Modi’s government, which had championed the locally developed shot.

Bharat Biotech Chairman Krishna Ella had previously slammed those who questioned Covaxin, and this week told a conference that WHO approval took so long because of the vaccine’s image being harmed by criticism. 

According to The Lancet, more research is needed to determine the vaccine’s long-term safety and effectiveness, as well as its ability to protect against severe disease, hospitalisation, and death, and its ability to fend off delta and other variants of concern.