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Allergic Reactions Including Anaphylaxis After Receipt of the First Dose of Pfizer-BioNTech COVID-19 Vaccine – United States, December 14-23, 2020

Our take —

The data here, from 1,893,360 first-dose vaccinees in the US through December 23, 2020, are reassuring and offer no surprises: the Pfizer/BioNTech COVID-19 vaccine is well-tolerated, and allergic reactions are rare. In the few cases of anaphylaxis reported here, most (17/21) had a history of allergic reactions, including prior anaphylaxis. These findings reinforce the current practice of screening potential vaccinees for previous serious allergic reactions prior to their receipt of the vaccine.

Study design

Other

Study population and setting

This study summarized the data available in the CDC’s Vaccine Adverse Event Reporting System (VAERS) for allergic reactions to the Pfizer/BioNTech COVID-19 vaccine immediately following its FDA Emergency Use Authorization (EUA) on December 11, 2020. Data for 1,893,360 first-dose vaccinees in the United States through December 23, 2020 are summarized.

Summary of Main Findings

175 cases of suspected allergic reactions were initially identified amongst the 1,893,360 recipients. Upon further investigation of these cases, 61 were found not to be allergic reactions, 83 were ultimately found to be non-anaphylactic allergic reactions (for a rate of 43.8 per 1 million first-dose vaccinees), and 21 were found to be anaphylaxis (for a rate of 11.1 per 1 million first-dose vaccinees).

72 of the 83 non-anaphylactic reactions were deemed non-serious, and included rash, pruritis (itchiness), and mild respiratory symptoms. 75 of the 83 non-anaphylactic reactions occurred in females. The median age was 43 years, and the median time to onset following vaccines administration was 12 minutes.

17 of the 21 anaphylactic reactions had a history of allergies (to medical products, food, bee stings, etc.), including 7 with a history of anaphylaxis. 19 of the 21 cases of anaphylaxis occurred in females. The median age was 40 years, and the median time to onset following vaccine administration was 13 minutes.

No vaccine-related deaths were recorded, and all patients for whom records were available fully recovered.

Study Strengths

Despite the short time window of approximately 2 weeks, records from nearly 2 million vaccinees were available for analysis, providing a cohort much larger than those available in clinical trials. The individual reports were scrutinized appropriately based on current guidelines for reporting of these events.

Limitations

At the time of this study, those receiving the vaccine under the EUA had only received the first dose; thus, data regarding allergic reactions immediately following the second dose were unavailable. Additionally, data collected only through spontaneous self-reporting (as was the case here) is not as reliable as that which is collected during closely-monitored clinical trials, and thus should be interpreted appropriately.

Value added

This study provides a timely, succinct snapshot of the rate of allergic reactions to the Pfizer/BioNTech COVID-19 vaccine immediately following its EUA approval and initial administration outside of clinical trial protocols.

This review was posted on: 12 February 2021