UK regulators say people who have a "significant history" of allergic reactions shouldn't receive the new Pfizer-BioNTech coronavirus vaccine.
Officials say they need time to 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, the nation's medicines regulator.
"As is common with new vaccines, the MHRA has 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."