A day after Vaccine Day in the U.K. regulators there are advising people who have a significant history of allergic reactions not to receive the new Pfizer-BioNTech COVID-19 vaccine while they investigate two adverse reactions that occurred Tuesday.

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.”

Dr June Raine is head of the Medical and Healthcare Products Regulatory Agency in Britain.

She told a British Parliamentary committee about the two allergic reactions which took place during the first day of Britain’s mass vaccination program.

Raine also pointed out, these type of reactions did not occur during the very extensive clinical trials leading up to approval of the vaccine.