Hyderabad, As part of human trials of Covaxin, India's first indigenous Covid-19 vaccine, two volunteers were given its first dose at the Nizam's Institute of Medical Sciences (NIMS) on Monday, doctors said.

The healthy volunteers, who were administered the first dose of the vaccine in the morning, were stable. "Both are stable and we have not found any reaction or side-effects," said Dr G. Srinivas, a member of the research team conducting the clinical trials.

The volunteers will remain under the observation of a team of doctors till Tuesday. They will be sent home but their condition will be remotely monitored by the doctors for 14 days.

The NIMS is one of the 12 institutes selected by the Indian Council of Medical Research (ICMR) for Phase-I clinical trials of the vaccine.

Hyderabad-based Bharat Biotech had announced on July 17 that the Phase-I clinical trials began across the country on July 15.

"This is a randomised, double-blind, placebo-controlled clinical trial in 375 volunteers in India," the company had said.

The vaccine maker had announced on June 29 that it successfully developed Covaxin in collaboration with the ICMR and National Institute of Virology (NIV).

The SARS-CoV-2 strain was isolated in NIV, Pune and transferred to Bharat Biotech. The indigenous, inactivated vaccine was developed and manufactured in Bharat Biotech's high containment facility located in Genome Valley, Hyderabad.

NIMS doctors said as many as 60 volunteers had enrolled for the clinical trials. They were screened and the healthy volunteers were selected and their reports were sent to ICMR, which finalised the fit volunteers based on different parameters.

Dr Srinivas said more volunteers would be administered dose as part of the clinical trial. "We will continue the Phase-I trials as per the sample size given by the ICMR and Bharat Biotech," he told reporters without specifying the numbers.

The Phase-I clinical trials are likely to go on for 28 days, after which the ICMR and the Drug Controller General of India (DGCI) would accord permission for Phase-II trials.

The ICMR said Phase-I would have around 375 subjects across the country and Phase-II, 875.

Doctors say the trials may be completed in five phases including pre-clinical studies which Bharat Biotech has already completed.

Earlier, NIMS Director Dr K. Manohar said subjects would be administered two doses of the vaccine.

Each subject would be given the second dose of the same vaccine after 14 days.

For two days after administering the vaccine, the subjects would be monitored for two days in the ICCU at NIMS by a team of doctors, after which they would be sent home and monitored through video conference or phone.