Covid-19: Bharat Biotech cuts Covaxin phase-2 clinical trial size by half

Bharat Biotech has halved the size of the phase-2 clinical trial of its Covid-19 vaccine candidate Covaxin and would now test it on only 380 volunteers after it got good immunogenicity data from the phase-1 trials. 

The firm said volunteers did not complain of any major side effects apart from fever and body aches. The trial size for phase-1 and -2 trials was set at 1,125 candidates. Of this, 375 volunteers were vaccinated in phase-1. So, 750 were to be a part of the phase-2 studies. The company confirmed the phase-2 will test only 380 volunteers but refused to share details. 

For phase-2 studies, the firm is also testing the vaccine on children above 12 years of age. In phase-1, they only tested adults. 

Covaxin is based on an inactivated Sars-CoV-2 virus that is administered in two days with a gap of 14 days in between. The firm would release phase-1 and -2 studies’ data after the phase-2 testing is over. They have not published any interim data from the phase-1 trials. 

Experts said reducing the size of the phase-2 trials could expedite the process as the firm can move to phase-3 earlier, after the data from the studies are analysed and the regulator gives a nod. 

Gagandeep Kang, professor at Christian Medical College Vellore and a leading medical scientist in the country, said good immunogenicity data from phase-1  might have encouraged Bharat Biotech to club the data from phase-1 and an abbreviated phase-2.  “This can expedite the moving of the trial to phase-3, provided the firm had regulator approval,” she said. 

Sources said the Hydera-bad-based company was gearing up for a large-scale phase-3 study to test the efficacy of Covaxin and was planning to test around 30,000 people. Efficacy studies test how effective the vaccine is or how many people do not get the disease after being vaccinated.

Interestingly, earlier this month the drug regulator had asked the firm to make some changes to its proposal to conduct phase-3 trials. Bharat Biotech had shown interim data from its studies to the subject expert committee and also presented the protocol for phase-3 clinical trials. 

Bharat Biotech is developing Covaxin in association with the Indian Council of Medical Research and the National Institute of Virology.