New Delhi, Union Health Minister Harsh Vardhan on Sunday said that Covid-19 vaccines developed outside India will have to undergo bridging studies to prove their safety and immunogenicity in the Indian population.

"We are open to assessing the feasibility of introducing several Covid-19 vaccines in the country... However, all vaccines that have proven to be safe, immunogenic and efficacious in clinical trials outside India need to undergo bridging studies to prove their safety and immunogenicity in the Indian population as well," he said.

"Such studies are conducted with much smaller sample size and quickly. A similar approach will be adopted for Covid-19 vaccines which are developed outside the country," he said during his weekly webinar "Sunday Samvaad".

Harsh Vardhan's comment comes as several candidate drugs enter the final phase of testing and trials. Three potential vaccines are being tested in India, including Covishield, which was developed jointly by the Jenner Institute of the University of Oxford and pharma giant AstraZeneca.

Covishield is in Phase-2 and Phase-3 human trials and, if successful, will be mass produced by Pune-based Serum Institute of India (SII), one of the world's largest manufacturers of vaccines. Its trials in India are running at 17 locations across the country.

A UK media report earlier this month said Covishield, which is also being tested there, could be cleared by health regulators in that country by end-2020 and be rolled out within six months.

Besides, two other vaccine candidates are also being tested across the country.

Indigenous vaccine developer Bharat Biotech, in collaboration with the the Indian Council of Medical Research and the National Institute of Virology, is conducting Phase-1 and Phase-2 clinical trials of vaccine candidate COVAXIN.

The third vaccine candidate under human trial is ZyCoV-D, developed by Zydus Cadila. This candidate is now under Phase-1 and Phase-2 of clinical trials.

The World Health Organisation (WHO) released the 'Draft landscape of Covid-19 candidate vaccines', on September 30, in which it informed that as many as 191 vaccine candidates are in various stages of development across the globe. Among these, 41 have made their way into clinical trials while 10 have entered the third phase of clinical trials.