Covaxin, India’s homegrown Covid-19 vaccine, has shown 78 per cent protective efficacy against symptomatic infection and 93 per cent efficacy against severe disease, the vaccine’s developers said on Saturday making public clinical trial results.

Covaxin also shows 65 per cent efficacy against the highly-transmissible Delta variant of the coronavirus, the vaccine maker Bharat Biotech and the Indian Council of Medical Research (ICMR) said in a paper that is not peer-reviewed yet but posted online on a preprint server.

While Bharat Biotech and the ICMR had announced efficacy results earlier this year, this is the first time they have released details of the trial on over 25,000 volunteers in hospitals across the country.

The paper shows that among the 130 symptomatic Covid cases detected during the trial, 24 patients had received the vaccine and 106 had received a placebo, or a sham injection. This 24:106 distribution of the symptomatic patients translates into 78 per cent efficacy against symptomatic infections.

Among 16 patients who developed severe Covid-19, one had received the vaccine and 15 had received the placebo, implying 93 per cent efficacy against severe disease. Of the 50 patients found with the Delta variant, 13 were vaccine and 37 were placebo recipients.

The trial also observed 63 per cent efficacy against asymptomatic infections.

The vaccine was “immunogenic and highly efficacious against symptomatic and asymptomatic Covid-19 and variant-associated disease, particularly against severe disease in adults,” the researchers said. There were no cases of anaphylaxis (a severe allergic reaction) or vaccine-related deaths in the study.

Covaxin, based on an inactivated (killed) virus, was jointly developed by the ICMR and Bharat Biotech. The company said the safety, immunogenicity and efficacy results from the trial will help support its applications for regulatory approval of the vaccine in other countries.

India’s Covid-19 vaccination campaign currently relies on Covishield — the AstraZeneca vaccine produced by the Serum Institute of India — and Covaxin. But around 90 per cent of the recipients have received Covishield because of Serum’s larger production capacity.