The Lancet study on Covaxin was funded by Bharat Biotech and the ICMR.
Covaxin, the coronavirus vaccine developed by the government's medical research agency and Bharat Biotech, was found to have a 77.8 per cent efficacy rate against symptomatic COVID-19 in a long-awaited analysis published in The Lancet. The study also found it to be 65.2 per cent effective against the more dangerous Delta variant of the coronavirus in its preliminary analysis but said further investigations are necessary to confirm it.
Covaxin, which uses traditional, inactivated-virus technology, "induces a robust antibody response" two weeks after two doses are given, The Lancet said in a statement. No severe-vaccine-related deaths or adverse events were recorded during a randomized trial involving 24,419 participants aged 18-97 years between November 2020 and May 2021 in India, the medical journal said.
"Efficacy against any severity of COVID-19 with onset 14 days after the second vaccination was 77.8 per cent... Our preliminary analysis found an efficacy of 65.2 per cent against the Delta variant, but further investigations are necessary to confirm clinical efficacy against this variant and others," the study said.
The interim study, which was funded by Bharat Biotech and the Indian Council of Medical Research and partly authored by officials at both bodies, is in line with the company's earlier efficacy and safety announcements and may help end the controversy surrounding the shot's early authorisation in January in India and concerns in some countries.
At the time, the shot had yet to clear final-stage trials, prompting widespread hesitancy in the early weeks of immunization drive. Since then more than 100 million doses of Covaxin have been deployed across India and last week the World Health Organization added the inoculation to its list of Covid vaccines authorized for emergency use.
The decision had been delayed as the advisory group sought additional clarifications from Bharat Biotech before conducting a final risk-benefit assessment for the vaccine's global use.
WHO's Strategic Advisory Group of Experts on Immunization also recommended Covaxin's use in two doses, with an interval of four weeks, in age groups 18 and above. These recommendations are in line with the company's guidance.
The WHO's approval and the Lancet study could also pave the way for India to commit supplies to the COVAX global vaccine sharing effort, which is co-led by the UN body and aims to provide equitable access to shots for low- and middle-income countries.
(With inputs from agencies)