Anaphylaxis cases reported after first dose of Pfizer-BioNTech COVID-19 vaccine in US surveillance

A surveillance report described a case series of allergic reactions, including anaphylaxis, occurring in individuals in the United States who received the first dose of the Pfizer-BioNTech COVID-19 vaccine between December 14 and 23, 2020. The report confirmed that cases of anaphylaxis were identified, but it did not provide the total number of cases, the total number of vaccine doses administered during the surveillance period, or any comparator data. Consequently, an incidence rate or relative risk could not be calculated.

The primary safety finding was the reporting of anaphylaxis as a serious adverse event. The report did not provide details on the severity grading of reactions, time to onset, management, or outcomes for the affected individuals. Information on other allergic reactions and overall tolerability was not reported.

Key limitations of this evidence include its design as an early surveillance case series without a control group. The absence of denominator data (total doses administered) prevents calculation of incidence, making it impossible to contextualize the risk. The funding sources and potential conflicts of interest were not reported.

For practice, this report serves as an early signal from post-authorization safety monitoring. It underscores the importance of having appropriate medical support and emergency protocols available at vaccination sites. The findings should be interpreted with caution until more robust, quantitative data from larger cohorts or controlled studies become available to properly assess the frequency and risk factors for this rare event.