What is the risk of anaphylaxis after vaccination in children and adults?

Published Online: October 6, 2015

Anaphylaxis is a potentially life-threatening allergic reaction, which can occur after many different exposures, e.g., food, venom, drugs, or vaccines. For context, each year in the United States, more than 100 million people receive influenza or other vaccines. Virtually all vaccines have the potential to trigger anaphylaxis. However, the magnitude of the risk of anaphylaxis after vaccination has not been well described.

In a report recently published in The Journal of Allergy and Clinical Immunology (JACI), McNeil and colleagues used data collected on more than 9 million subjects in the CDC’s Vaccine Safety Datalink (VSD is a collaborative project between CDC and 9 integrated US healthcare organizations), to determine rates of anaphylaxis after all vaccines combined and for selected individual vaccines in children and adults. They included all patients with a record of a vaccination during January 2009 through December 2011. A search of the VSD databases for specific computerized diagnostic codes and epinephrine prescriptions identified potential anaphylaxis cases following any vaccine. These patients’ medical records were reviewed to confirm that they met standardized criteria for anaphylaxis that had been triggered by vaccination.       

The researchers identified 33 confirmed vaccine-triggered anaphylaxis cases that occurred after receipt of more than 25 million vaccine doses. Ages of these patients ranged from 4 to 65 years, one patient was hospitalized and none died. A majority (85%) had pre-existing atopic disease (3 with prior anaphylaxis, 16 with asthma, and 9 with specific prior allergies). The rate of anaphylaxis was calculated to be 1.31 per million vaccine doses for all vaccines combined and 1.35 per million doses for seasonal inactivated influenza vaccines. The rate did not vary significantly by age, and there was a nonsignificant female predominance.

The authors found the risk of anaphylaxis after all vaccines, and specifically inactivated influenza vaccines, is rare in all age groups, with a rate of 1-2 per million vaccine doses administered. Despite its rarity, anaphylaxis is a potentially life-threatening medical emergency that vaccine providers need to be prepared to treat.  

The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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