Researchers have advised that the post-vaccination observation period after administration of the Pfizer-BioNTech COVID-19 vaccine should be 15 to 30 minutes long.
Reporting in JAMA, the researchers present an analysis of adverse events following the first dose of the Pfizer-BioNTech vaccine which were reported through the US Vaccine Adverse Event Reporting System (VAERS).
From December 14 to 23, 2020, of 1,893,360 first doses of the vaccine, 21 case reports met Brighton Collaboration case definition criteria for anaphylaxis, corresponding to an estimated rate of 11.1 cases per million doses administered. Seventeen (81%) had a history of allergies.
Four patients (19%) were hospitalised (including 3 in intensive care), and 17 (81%) were treated in an emergency department. Twenty (95%) were discharged home or had recovered at the time of reporting. No deaths from anaphylaxis were reported.
Median interval from vaccine administration to symptom onset was 13 minutes (range, 2-150 minutes.
The most common presentations were urticaria, angioedema, rash, and a sense of throat closure.
Commonly reported symptoms in nonanaphylaxis allergic reactions included pruritus, rash, throat irritation, and mild respiratory symptoms.
The authors advise that vaccination centres should ensure supplies are available to manage anaphylaxis and that post-vaccination observation periods should be set at 15 or 30 minutes.