Covaxin Phase I trial results show vaccine is safe, generates immune response

In a preprint paper, researchers from Bharat Biotech, ICMR, AIIMS have reported the results of the trial on 375 participants.

The Covaxin vaccine | www.bharatbiotech.com | File photo

New Delhi: Results of the phase I trial of Covaxin — the indigenous Covid-19 vaccine developed through a partnership between Indian Council of Medical Research (ICMR) and Bharat Biotech — show that the vaccine is safe and immunogenic. One adverse event was reported during the trial but it was found to be unrelated to the vaccine, according to the researchers.

“Reactogenicity was absent in the majority of participants, with mild events. The majority of adverse events were mild and were resolved. One serious adverse event was reported, which was found to be unrelated to vaccination. All three vaccine formulations resulted in robust immune responses comparable to a panel of convalescent serum,” researchers from Bharat Biotech, ICMR, AIIMS (New Delhi and Patna) and several other institutes reported in a preprint paper on MedRxiv. 

For the phase I trial, a total of 375 participants were randomised equally to receive the vaccine formulations or a placebo. Healthy male and non-pregnant female volunteers aged between 18 and 55 years were enrolled for the study.

Bharat Biotech is currently conducting phase III trials of the vaccine. It has also applied to the Drugs Controller General of India for an emergency use authorisation for the vaccine along with Pfizer and Serum Institute of India (SII). 

Both Bharat Biotech and SII have been asked to submit more data to the subject expert committee of the Central Drugs Standard Control Organisation (CDSCO). 

Covaxin has been made from an inactivated SARS-CoV2 virus and sequenced at the Indian Council of Medical Research’s National Institute of Virology (NIV).

Adverse event in the placebo group

The paper talks about one serious adverse event in the course of the trial. “One serious adverse event was reported in the 6 μg with Algel group. The participant was screened on July 25th and vaccinated on July 30th,” the paper states. “Five days later, the participant reported symptoms of Covid-19 and was found to be positive for SARS-CoV-2 (by a nucleic acid test). The symptoms were mild in nature, but the patient was admitted to the hospital on August 15th. The participant was discharged on August 22nd following a negative nucleic acid result. The event was not causally associated with the vaccine. No other symptomatic SARS-CoV-2 infections were reported between day 0 and 75.”

The researchers are also clear that the data they have reported “do not permit efficacy assessments”. 

“The evaluation of safety outcomes requires more extensive Phase 3 clinical trials,” they add. “Last, we evaluated an accelerated schedule (vaccination occurred 2 weeks apart) and did not include a routine schedule (vaccination occurring 4 weeks apart). The latter schedule is being evaluated in Phase 2.”