By Ashish Srivastava

New Delhi, Jan 7 (IANS): Hyderabad-based vaccine manufacturer Bharat Biotech has concluded the recruitment of volunteers for the phase III trials of its Covid vaccine, Covaxin, on Thursday after achieving the sample size it had promised to the ethics committee. The firm has achieved the targeted number of volunteers, which is 25,800 participants, in total.

The recruitment was supposed to be concluded by December 31 but was extended by a week since it was short of 4,000 volunteers that time.

Dr. Sanjay Kumar Rai, head of community medicine and principal investigator of the trial at All India Institute of All India Institute of Medical Sciences (AIIMS), Delhi told IANS that the recruitment for the phase III study is closed now.

"Around 99 per cent of the promised target was achieved by AIIMS. However, we have finished our enrollment after achieving the target in toto," he said.

Dr. C Prabhakar Reddy, principal investigator of Covaxin's phase III clinical trial at Nizam's Institute of Medical Sciences, Hyderabad, said that a few sites missed their individual target by a few numbers.

"However, the sites which over achieved their target compensated for it," he added.

While many sites struggled to find volunteers for the phase 3 study, a few sites registered them in abundance. AIIMS Patna, one of the clinical sites for Covaxin undertook around 1,400 subjects despite its individual target set at 1,000.

IANS had earlier reported that AIIMS Delhi and several other clinical sites were facing the dearth of volunteers since people were unwilling to participate in the exercise, hoping that they would receive the vaccine anyway once it is rolled-out by the government.

The phase III study of the Covaxin, which initially spanned at 25 clinical sites across the country, inducted several more sites in the last week of December since many sites were unable to find the volunteers for the study.

Dr. Dhananjay Lad, co-investigator of the trial at Redkar Hospital, Goa, told IANS that the trial was extended to around 30 clinical sites.

"A few sites were also removed in the process because of several reasons. One of the reasons was inability to enroll a bare minimum number of participants," he said.

The trial was started with three sites each in Uttar Pradesh (Aligarh Muslim University), West Bengal (ICMR-National Institute of Cholera and Enteric Diseases) and Tamil Nadu (Directorate of Public Health and Preventive Medicine) on November 10.

Covaxin has been given approval for restricted emergency use by India's drug regulator. While the efficacy of the vaccine is yet to be determined, it was given a go-ahead by the Drug Controller General of India (DCGI) citing public interest.

Covaxin is indigenously developed by the Bharat Biotech, in collaboration with the Indian Council of Medical Research (ICMR).