This article is more than 5 years old. Information may no longer be current.

Anaphylaxis rare after vaccinations

Anaphylaxis after vaccination appeared rare, according to results of a data analysis.

“Vaccination is one of the best ways parents can protect infants, children and teens from 16 potentially harmful diseases,” Michael M. McNeil, MD, MPH, of the immunization safety office and division of healthcare quality promotion at the National Center for Emerging and Zoonotic Infectious Diseases at the CDC, said in a press release. “This is a good time to remind parents that vaccines are safe and effective — the odds of having an anaphylaxis-related reaction following the administration of a vaccine are very slim.”

McNeil and colleagues used data from the Vaccine Safety Datalink to identify individuals (median age, 17 years; range, 4-65) who underwent vaccination between January 2009 and December 2011.

The researchers reviewed patient data to identify specific diagnostic and procedure codes, as well as epinephrine prescriptions, to identify anaphylaxis cases that followed vaccine receipt. In these cases, McNeil and colleagues reviewed patients’ medical records to confirm they met standard Brighton Collaboration criteria for anaphylaxis triggered by vaccination.

Researchers used the data to calculate the incidence of anaphylaxis after selected individual vaccines, as well as after all vaccines combined.

They identified 33 cases of anaphylaxis triggered by vaccines after more than 25.1 million vaccine-administered doses. They calculated an anaphylaxis rate of 1.31 (95% CI, 0.9-1.84) per 1 million vaccine doses.

Researchers identified 10 cases of anaphylaxis after receipt of the influenza vaccine, equating to a rate of 1.35 (95% CI, 0.65-2.47) per 1 million doses, and two cases of anaphylaxis after receipt of the inactive monovalent influenza vaccine, equating to a rate of 1.83 (95% CI, 0.22-6.63) per 1 million doses).

Time to symptoms was 30 minutes or less in eight cases; between 30 minutes and 2 hours in eight cases; between 2 hours and 4 hours in 10 cases; between 4 hours and 8 hours in two cases; and the following day in one case. Time to symptoms was undocumented in four cases.

The researchers observed no significant difference in anaphylaxis based on study participants’ age or sex.

Two children aged younger than 4 years demonstrated anaphylaxis symptoms, but researchers determined neither were caused by vaccination. One was caused by amoxicillin and the other was caused by food allergies.

“Despite its rarity, anaphylaxis is a potentially life-threatening medical emergency that vaccine providers need to be prepared to treat,” McNeil and colleagues wrote. – by Jeff Craven

Disclosure: The researchers report research or travel support from the CDC, GlaxoSmithKline, MedImmune, the NIH, Novartis, Nuron Biotech, Merck, Pfizer, Protein Science and Sanofi Pasteur.