Nearly 1,000 people to receive doses of experimental Covid-19 vaccine under Phase 3 trial

At least 370 participants have so far received the doses of the upcoming Covid vaccine candidate, Covaxin, at PGIMS Rohtak — one of 26 designated trial sites across

At least 370 participants have so far received the doses of the upcoming Covid vaccine candidate, Covaxin, at PGIMS Rohtak — one of 26 designated trial sites across the country. Experts overseeing the trial said they will administer another 750 odd doses of the vaccine to the same number of participants by December-end, as part of the ongoing Phase 3 of the trial of the vaccine.

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About 25 new participants per day will be administered their first shot of the vaccine over this month, followed by a booster dose after 28 days. In Rohtak, the sample size for Phase 3 trials is expected to be around 1,000 people, officials said, while about 26,000 people will participate nationally.

Covaxin is an indigenous Covid-19 vaccine, which is being developed by Bharat Biotech and ICMR’s National Institute of Virology, Pune. It is one of the two Indian vaccine candidates that have received the Drug Controller General of India’s nod to proceed with Phase 3 trials.

Phase 1 of the Covaxin trials, which began at Rohtak in mid-July, involved 10 participants — all of whom were healthy adults, between the ages 18 and 55, and without any prior history of SARS-Cov-2 infection. “After we ruled out acute side effects, we proceeded with Phase 2 trials in September to test the immunogenicity of the vaccine. In this phase, we gave Covaxin shots to about 130 people between ages 12 and 65. Some also had comorbidities such as diabetes and asthma, but well within control. Now, in ongoing Phase 3 trials, we are administering the vaccine in the realm of real life,” said Dr Dhruv Chaudhury, nodal officer for Covid-19 management in the state and co-principal investigator of the Covaxin trials at PGIMS Rohtak.

At least 30 percent of the Phase 3 trial’s sample population, Chaudhury said, will include people having pre-existing comorbidities and health workers. “All participants have been informed that they must continue to remain cautious and maintain social distancing even after receiving the shot, as neutralising antibodies are not produced immediately but can take up to 42 days to develop. We take blood samples at 28 days and 42 days after the first shot to check for the presence of antibodies” Chaudhury said.

Chaudhury said that Phase 3 trials for Covaxin are expected to be completed by mid-January. He did not, however, comment on when interim data regarding vaccine efficacy (from Phase 1 and Phase 2 of the trial) would be shared.

Covaxin is an “inactivated” vaccine, which relies on using samples of the SARS-Cov-2 virus that have been isolated at the National Institute of Virology, Pune. “The vaccines consist of virus particles which have been rendered inactive or are unable to replicate. However, the antigens will give a signal to the immune system to produce immunoglobulins or antibodies. This is different from the other Indian vaccine candidates, which does not contain any attenuated virus particles, and instead only relies on messenger RNA, or genetic code of the spike proteins of the virus, to signal our immune system,” explained another co-investigator at PGIMS Rohtak, who did not wish to be identified.