COVID-19: What do the allergic reaction cases mean for Pfizer’s vaccine

UK officials said there have been two reports of anaphylaxis and one report of a possible allergic reaction since rollout began.

Britain’s medicines regulator has advised people with a history of significant allergies not to get the Pfizer-BioNTech COVID-19 vaccine after two people reported adverse reactions on the first day of its rollout in the UK. Here are some questions and answers about the cases and what they might mean.

What exactly happened?

UK officials said there have been two reports of anaphylaxis and one report of a possible allergic reaction since rollout began. Anaphylaxis can cause throat swelling, breathing trouble and difficulty swallowing, according to the American Academy of Allergy, Asthma & Immunology. Anaphylaxis is an overreaction of the body`s immune system, which the UK National Health Service describes as severe and sometimes life-threatening.

Who should not get the vaccines?

British regulators initially responded by saying anyone with a history of a significant allergic reaction to a vaccine, medicine or food should not take the shot. An adviser to the group later said it was ‘tweaking’ advice in part to say a food allergy was not a risk.

Late on Wednesday, the UK regulator said anyone with a history of anaphylaxis to a vaccine, medicine or food should not get the vaccine. Pfizer had excluded people with a history of significant adverse reaction to vaccines or its vaccine`s ingredients from late-stage trials.

What do doctors say?

Some praised UK regulators’ caution, while others said broad restrictions were not warranted by available evidence.

“For the general population, this does not mean that they would need to be anxious about receiving the vaccination,” said Stephen Evans, a professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine