People with a history of significant allergic reactions should have been warned not to have the Pfizer/BioNTech Covid jab, UK medicines regulator has said.
It came after two NHS workers had allergic reactions on Tuesday.
The advice applies to those who have had reactions to medicines, food or vaccines, the Medicines and Healthcare products Regulatory Agency said.
The health workers, who are understood to both have a history of severe allergic reactions, were among thousands to receive the vaccine on the first day of the Covid-19 mass vaccination programme.
A further report of a possible allergic reaction following immunisation was also received by the MHRA.
Dr June Raine said a group including experts on allergy and clinical immunology was convened on Wednesday to consider any possible mitigation to the “rare risk of anaphylaxis”.
Any person with a history of anaphylaxis to a vaccine, medicine or food should not receive the Pfizer BioNTech vaccine. A second dose should not be given to anyone who has experienced anaphylaxis following administration of the first dose of this vaccine," Dr Raine said.
Peter Openshaw, past-president of the British Society for Immunology and professor of experimental medicine at Imperial College London, said: “As with all food and medications, there is a very small chance of an allergic reaction to any vaccine.
“However, it is important that we put this risk in perspective. The occurrence of any allergic reaction was one of the factors monitored in the phase three clinical trial of this Pfizer/BioNTech Covid-19 vaccine, the detailed data from which was released yesterday.
Doses are expected to be delivered to around 200 GP surgeries initially to allow them to start on Tuesday. The over-80s will be invited first.
Once the first 200 GP practices have received their doses the programme will be expanded out to more than 1,000 surgeries - with each local area having a designated site.
Meanwhile, anyone scheduled to receive the vaccine from now will be asked about their history of allergic reactions before getting the jab.