�U.K. regulators said Wednesday that people who have a �significant history� of allergic reactions shouldn�t receive the new Pfizer-BioNTech vaccine while they investigate two adverse reactions that occurred on the first day of the country�s mass vaccination program.

Professor Stephen Powis, national medical director for the National Health Service in England, said health authorities were acting on a recommendation from the Medical and Healthcare Products Regulatory Agency.

�As is common with new vaccines the MHRA have advised on a precautionary basis that people with a significant history of allergic reactions do not receive this vaccination after two people with a history of significant allergic reactions responded adversely yesterday,� Powis said in a statement. �Both are recovering well.�

The comments came as Dr. June Raine, head of the MHRA, told a Parliamentary committee that regulators had received reports of two allergic reactions from the vaccine.

�We know from the very extensive clinical trials that this wasn�t a feature,� she said. �But If we need to strengthen our advice, now that we have had this experience with the vulnerable populations, the groups who have been selected as a priority, we get that advice to the field immediately.

Raine�s comments came as part of a general discussion of how her agency will continue to monitor people who receive the vaccine authorized for emergency use last week.

(AP)