CDC Study Finds Anaphylaxis Rare After Vaccinations, With No Fatalities Interview with:
Michael M. McNeil, MD, MPH

Centers for Disease Control and Prevention
Atlanta, GA

Medical Research: What is the background for this study? What are the main findings?

Dr. McNeil : Anaphylaxis is an uncommon potentially life-threatening allergic reaction which can occur immediately (usually within minutes) after exposures to food, drugs, venom and vaccines. More than 100 million people in the U.S. receive vaccinations each year. Most vaccines have the potential to trigger anaphylaxis, but the rates at which it occurs after vaccination are not well known. The CDC study examined data from the Vaccine Safety Datalink (VSD), a collaborative project between CDC and 9 integrated healthcare organizations, which contains vaccination records on more than 9 million patients. The study sought to determine the rates of anaphylaxis after all vaccines combined and some individual vaccines including seasonal influenza vaccines given to children and adults.  Patients studied received vaccinations between January 1, 2009 – December 31, 2011.  Electronic medical record data was screened for patients with specific diagnostic codes for anaphylaxis or who had received epinephrine prescriptions as a treatment for potential anaphylaxis. Researchers were able to look at data from 25,173,965 vaccinations during 17,606,500 visits to healthcare providers.

The researchers identified 33 confirmed vaccine-triggered anaphylaxis cases that occurred after more than 25 million vaccine doses. The rate of anaphylaxis was calculated at 1.31 per million doses for all vaccines, and 1.35 per million for seasonal inactivated influenza vaccines. Patients ranged in age from 4 to 65 with a median age of 17. None of the patients with anaphylaxis were below the age of 4 years old. Only one of the 33 patients was hospitalized, and none died as a result of anaphylaxis. A majority (85%) of the case-patients had pre-existing atopic disease including previous anaphylaxis, asthma, and allergies.

Medical Research: What should clinicians and patients take away from your report?

Dr. McNeil : Our study which is based on a very large population receiving currently used vaccines, confirms the rarity of anaphylaxis occurring in all age groups after vaccination overall and after specific vaccines. Providers and patients can be reassured by these results. Although anaphylaxis after vaccination is rare, its immediate onset (usually within minutes) and life-threatening nature require that all personnel and facilities providing vaccinations have procedures in place for anaphylaxis management.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. McNeil : Future epidemiologic research on anaphylaxis after vaccination with the goal to strengthen the evidence supporting recommendations for its prevention and management will require large study populations.


Risk of anaphylaxis after vaccination in children and adults
McNeil, Michael M. et al.

Journal of Allergy and Clinical Immunology
Published Online:October 06, 2015

Michael M. McNeil, MD, MPH (2015). CDC Study Finds Anaphylaxis Rare After Vaccinations, With No Fatalities

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