Participants with a “history of severe adverse reaction associated with a vaccine and/or severe allergic reaction (eg, anaphylaxis) to any component of the study intervention(s)” were not included in the pool of 44,000 trial volunteers.
According to the US Food and Drug Administration's evaluation of the Pfizer data, there was a slight increase in events that may be considered allergic reactions in the vaccine group. The FDA’s independent analysis said “A slight numerical imbalance of adverse events potentially representing allergic reactions, with more participants reporting hypersensitivity-related adverse events in the vaccine group (137 [0.63%]) compared with the placebo group (111 [0.51%])”
Some background: The UK issued new guidance on Wednesday, now advising that people with a “significant history of allergic reactions” not receive the Pfizer/BioNTech coronavirus vaccine after two health workers who received the vaccine suffered allergic reactions.
British health authorities are conducting an investigation into the two incidents. In a statement, Pfizer said “As a precautionary measure, the MHRA has issued temporary guidance to the NHS while it conducts an investigation in order to fully understand each case and its causes. Pfizer and BioNTech are supporting the MHRA in the investigation.”
Both staff members reportedly had a significant history of allergic reactions and carried adrenaline autoinjectors, according to PA Media. Thousands overall are believed to have been vaccinated in the UK on Tuesday.
The FDA's vaccine advisory group is meeting on Thursday to discuss a possible emergency use authorization of the Pfizer-BioNTech Covid-19 vaccine in the US.