A Pfizer spokeswomen did not immediately respond to a request seeking comment
Any vaccine maker, including Pfizer Inc, which has sought emergency-use authorisation for its COVID-19 shot in India, must conduct a local "bridging" safety and immunogenicity study to be considered for the country's immunisation programme, a senior government official told Reuters.
Serum Institute of India, manufacturer of the vaccine developed by AstraZeneca Plc and Oxford University, has done a similar study on more than 1,500 people over months before seeking and receiving emergency approval in the country.
There were reports that Pfizer had sought an exception when last month it became the first company to seek emergency-use approval in India for its vaccine already in use overseas. The company has not attended subsequent meetings called by the country's drugs regulator.
"As of now, the pre-condition for any vaccine to be implemented in India is that you have to do a bridging trial," Vinod K Paul, who heads a government panel on vaccine strategy, said in an interview.
A Pfizer spokeswomen did not immediately respond to a request seeking comment.
Mr Paul also said Russia's Sputnik V, a shot undergoing last-stage trials in India, will soon apply for emergency-use approval in the country.
No vaccine maker will be given indemnity by the government should something go wrong, Mr Paul said. Serum Institute had written to the government seeking indemnity. AstraZeneca has said it has received such indemnity in many other countries.