Bharat Biotech’s coronavirus vaccine, Covaxin, was well tolerated and induced enhanced immune response with neutralising antibodies among participants, according to preliminary data of its Phase 1 trials, published in The Lancet journal on Friday.

The study found that there were no major adverse effects of the vaccine, with participants experiencing common side effects such as pain at injection site, headache, fatigue and fever and nausea. One event of adverse effect was noted, but was unrelated to the vaccine, the study funded by Bharat Biotech said. Earlier this week, Bharat Biotech had advised people not to take the vaccine if they had allergies, fever, bleeding disorder or were on blood thinners.

“The vaccine was well tolerated in all dose groups with no vaccine-related serious adverse events,” the study noted.

The Phase 1 trials of Covaxin took place between July 13 and 30 last year. It involved 375 participants, of which 100 each were assigned to three different groups that were administered different vaccine doses, according to the report published in The Lancet. The control group was formed by 75 participants. The trial took place at 11 hospitals across nine states in India and the participants were aged between 18 to 55 years old.

Developed by Bharat Biotech in collaboration with the Indian Council of Medical Research and the National Institute of Virology in Pune, the vaccine was granted emergency use authorisation in clinical trial mode by the government. However, it raised concerns among experts as the Central Drugs and Standards Committee approved it for use before completing the third phase human trials.

Earlier this month, doctors of Delhi’ Ram Manohar Lohia Hospital demanded that they be given Serum Institute’s Covishield vaccine instead of Covaxin as the former has completed its Phase 3 trials. Organisations of survivors of 1984 Bhopal gas tragedy have also demanded to stop the ongoing trial of Bharat Biotech’s vaccine in the Madhya Pradesh capital, following death of a volunteer, allegedly during the clinical trial of the vaccine.

However, Indian Council of Medical Research chief Balram Bhargava has defended the drug controller decision to grant approval to the vaccine.