UK to refine allergy warning on Pfizer Covid vaccine

London, United Kingdom - The UK's medicine regulator is reviewing the cases of two people who suffered adverse reactions to the jab.

Britain's medicine regulator warned people with significant allergies not to get Pfizer-BioNTech's Covid-19 vaccine after two people suffered adverse reactions, but was set to give more detailed guidance on Wednesday based on reviews of those cases.

Starting with the elderly and frontline workers, Britain began mass vaccinating its population on Tuesday, part of a global drive that poses one of the biggest logistical challenges in peacetime history.

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National Health Service medical director Stephen Powis said the advice had been changed as a precaution after two NHS workers reported anaphylactoid reactions from the vaccine.

"Two people with a history of significant allergic reactions responded adversely yesterday," Powis said. "Both are recovering well."

The Medicines and Healthcare Products Regulatory Agency (MHRA) initially advised anyone with "a history of a significant allergic reaction to a vaccine, medicine or food" to avoid taking the vaccine.

However, by the end of Wednesday that guidance was set to be refined after discussions with experts on the nature of the reactions.

"We're tweaking advice to make it very clear that if you've got a food allergy, you're not more at risk," Imperial College London's Paul Turner, an expert in allergy and immunology who has been advising the MHRA on their revised guidance, told Reuters.

Pfizer and BioNTech said they were supporting the MHRA's investigation.

Last week Britain's MHRA became the first in the world to approve the vaccine, developed by Germany's BioNTech and Pfizer, while the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) continue to assess the data.

A top US official said on Wednesday that Americans with known severe allergic reactions may not be candidates for Pfizer's Covid-19 vaccine until more was understood about what had happened.

Canada's health ministry said it would look at the reported adverse reactions in Britain, but said adverse events were to be expected and would not necessarily change the risk/benefit of the shot, after the country approved the vaccine.

ALLERGIC REACTION

MHRA Chief Executive June Raine told lawmakers such allergic reactions had not been a feature of the Pfizer's clinical trials.

Pfizer has said people with a history of severe adverse allergic reactions to vaccines or the candidate's ingredients were excluded from their late stage trials, which is reflected in the MHRA's emergency approval protocol.

However, the allergic reactions may have been caused by a component of Pfizer's vaccine called polyethylene glycol, or PEG, which helps stabilise the shot and is not in other types of vaccines.