PURPOSE OF THE STUDY.
To estimate the incidence and clinical presentation of anaphylaxis as an adverse event after immunization through prospective active surveillance.
Children under age 16 years in the United Kingdom and Ireland with suspected anaphylaxis as an adverse event after immunization were reported to the British Pediatric Surveillance Unit (BPSU) over a 13-month period.
Pediatricians in the United Kingdom and Ireland were sent monthly cards inquiring about rare disorders including cases of children who may have had anaphylaxis after receiving an immunization. The cards were sent to BPSU. For those who did report a possible case, the physicians were asked to complete a more complete questionnaire (online or paper) about the presentation, diagnosis, management, and outcome of the case.
Overall, return rates for the monthly cards inquiring about rare disorders were 93.2% in the United Kingdom and 91.8% in Ireland. In all, 15 reports of possible anaphylaxis were made to the BPSU. Seven cases met the criteria for anaphylaxis as an adverse event after immunization. For 3 cases, the onset of symptoms occurred within 15 minutes of immunization; whereas 4 cases occurred 30 minutes or longer post immunization, with 1 case occurring 120 minutes later. The majority of children required treatment with intramuscular adrenaline and oral antihistamines. Two cases were associated with single-component measles vaccine with an incidence of 12.0 cases per 100,000 doses. Three cases were associated with human papillomavirus vaccine with an incidence of 1.4 cases per 1 million doses. Several of the children who had adverse reactions to human papillomavirus had underlying food allergy or idiopathic anaphylaxis. No anaphylactic events were reported due to routine infant and preschool immunizations despite 5.5 million vaccines being administered over the 13-month period.
Anaphylaxis due to immunization is a very rare adverse event. No cases of anaphylaxis after routine vaccination of infants and preschool children were reported over the 13-month period in which more than 5.5 million vaccines were administered. When anaphylaxis does occur, it may be delayed for some children, especially those who have concurrent allergic disease.
This study is a valuable addition to the existing evidence concerning vaccine safety. It provides reassurance for both health care professionals and families that an adverse event such as anaphylaxis is quite rare.
- Copyright © 2012 by the American Academy of Pediatrics