Covaxin, the coronavirus vaccine being developed by Bharat Biotech in collaboration with the Indian Council of Medical Research, was given the go-ahead for the third and final round of clinical trials on Thursday, NDTV reported. The study will cover 28,500 subjects aged 18 and above, the Hyderabad-based firm that makes the vaccines said.

Bharat Biotech had applied for permission for the third phase to the Drugs Controller General of India on October 2. The trials would be conducted in 19 sites, including Delhi, Mumbai, Patna and Lucknow, and across 10 states.

Savita Verma, principal investigator who leads the vaccine trial at PGI Rohtak, told The Economic Times that there were minor adverse reactions in some but overall the preliminary results showed that Covaxin is safe.

Drugs Controller General of India’s Subject Expert Committee recommended granting of permission to conduct phase three clinical trials for Covaxin after assessing data from phase one and two as well as animal challenge study. The nod is subject to a few minor amendments in how primary efficacy endpoint for symptomatic cases can be studied in the third phase, the drug regulator said.

“In continuation of the SEC meeting dated 05.10.2020, firm presented their data from Phase I and II along with animal challenge data in two species including NHP [National Health Portal] on the Inactivated Corona Virus Vaccine (BBV152) along with the proposal to conduct event driven Phase III clinical trial to assess the efficacy of the vaccine,” the DGCI said in a statement.

Covaxin, India’s first indigenous vaccine, is an inactivated vaccine created from a strain of the infectious SARS-CoV-2 virus. Inactivated vaccines use the killed version of the germ that causes a disease. It helps the immune system mount an antibody response towards virus.

Last month, Bharat Biotech had successfully conducted clinical trials of Covaxin on animals. The company said no adverse effects were seen in animals who were immunised with a two-dose regimen of the vaccine.

No vaccine has yet been approved for commercial use against the coronavirus, but over a dozen vaccines from more than 100 candidates globally are being tested on humans. The vaccines, which are currently in Phase 3 trials, are all administered by injection, according to the World Health Organization. The Serum Institute of India is conducting Phase 3 trials of a vaccine candidate developed by Oxford University and British pharmaceutical company AstraZeneca.