Revaccination and Adverse Event Recurrence in Patients With Adverse Events Following Immunization

The authors of this study assessed the risk of recurrence of adverse events following immunizations (AEFIs) after revaccination and sought to determine if skin test positivity in patients with suspected vaccine allergy was associated with AEFI recurrence.

This study included 588 participants in the Canadian Special Immunization Clinic (SIC) Network from June 2013 to September 2019 with AEFIs who required revaccination with the vaccine associated with the AEFI.

This was a prospective observational study where subjects were evaluated by standardized assessment and data collection on the participants. SIC Network guidelines were implemented by the physicians for evaluation and treatment of the patient. From 2013 to 2016, allergy skin testing was done for anyone with anaphylaxis or nonanaphylactic hypersensitivity starting less than 4 hours post vaccination and then in 2017 this was modified to less than 1-hour postvaccination. The participants were followed after revaccination.

Of the 588 participants included, there were 627 AEFIs assessed. Ninety one percent (570) of the AEFIs were in children less than 18 years of age. These AEFIs included immediate hypersensitivity (21%), large local reactions (18%), nonurticarial rash (8%), seizures (4%), and thrombocytopenia (2%). Eighty seven percent (513 of 588) of the participants were advised to revaccinate. Of those recommended and due for revaccination, 63% (299 of 477) were revaccinated. The AEFI recurrence in these patients was 10% (31 of 299) overall and then specifically 31% (15 of 49) for large local reactions and 7% (5 of 66) for immediate hypersensitization when compared with the original reaction. Skin testing was completed on 147 patients to assess risk of revaccination. The negative predictive value of allergy skin testing for AEFI recurrence was 96% overall. Participants with a positive skin testing were less likely to be recommended for revaccination and if revaccinated, they were more likely to experience AEFI recurrence compared with those with negative testing.

The study delineated revaccination and AEFI recurrence in 588 participants in the SIC Network. Of this study population, 63% who were recommended revaccination and due for revaccination actually received the vaccine, with a 10% recurrence of AEFI. The most common AEFI after revaccination was large local reactions. Furthermore, the participants who were diagnosed with vaccine allergy and underwent skin testing showed a good negative predictive value on the testing.

Vaccinations are a critical aspect of population health and vaccine hesitancy is a rising concern among pediatricians. When an adverse event follows immunization, this further raises vaccine hesitancy in caregivers and caution among providers. To properly counsel and treat patients requiring vaccine boosters and adherence to recommended vaccine schedules, it is imperative we understand the risks of recurrence of AEFIs and the availability of accurate diagnostic studies through allergy specialists. This study suggests that revaccination can often be successful, further emphasizing the need for collaboration with allergy specialists to delineate true vaccine allergy following a reaction.