Bharat Biotech’s Covid-19 vaccine Covaxin has an overall efficacy of 77.8% in symptomatic patients, interim phase 3 trial results published in medical journal The Lancet showed.

The results are in line with the pre-print data of the third phase of the vaccine trials published in July in the medical journal medRxiv.

In the data published on Thursday, vaccine efficacy of 79.4% was recorded in participants aged below 60 years and 66.2% in older people.

The efficacy was based on 130 symptomatic cases among 16,973 participants, who were initially seronegative (those who did not have detectable antibodies against Covid-19). Following the administration of the jabs, 24 cases were reported in the vaccine group and 106 in the placebo group.

Of these, 15 were severe Covid-19 cases in the placebo group and one was in the vaccine group. The study found Covaxin to be 93.4% effective against severe disease.

“Fifty samples overall tested positive for the delta variant, 13 in the vaccine group and 37 in the placebo group, giving a vaccine efficacy against delta variant disease of 65.2%,” the research said. “Nevertheless, further investigations are necessary to confirm this preliminary efficacy against the delta variant and other VOCs [variant of concern].”

No severe vaccine-related adverse events or deaths were reported among the trial participants.

“Generally, the apparent protection against severe Covid-19 is most crucial but the capability of preventing asymptomatic infection would also protect against mild disease, transmission, and eventually might lead to a reduction in subsequent cases of severe Covid-19,” the research said.

The trial was conducted on 25,798 participants, of whom 24,419 adults were randomly assigned to receive the vaccine doses or a placebo. The participants received the doses in 25 hospitals across the country.

The study however, highlighted that it involved only Indian participants, making its trial group less ethnically diverse.

Covaxin has been used in India since India began its immunisation drive on January 16. The vaccine, however, got the approval from the World Health Organization only on November 3.

The Drugs Controller General of India had granted approval for restricted emergency use to Covaxin in January. Covaxin and Oxford-AstraZeneca’s Covishield were the first Covid-19 vaccines to be approved in India.