While adverse events following immunization (AEFI) are frequent, there are limited data on the safety of reimmunizing patients who had a prior AEFI. Our objective was to estimate the rate and severity of AEFI recurrences.
We analyzed data from the AEFI passive surveillance system in Quebec, Canada that collects information on reimmunization of patients who had a prior AEFI. Patients with an initial AEFI reported to the surveillance system between 1998 and 2016 were included. Rate of AEFI recurrence was calculated as: number of patients with recurrence/ total number of patients reimmunized.
Overall, 1350 patients were reimmunized, of which 59% were less than 2 years old. The AEFI recurred in 16% (215/1350) of patients, of whom 18% (42/215) rated the recurrence as more severe than the initial AEFI. Large local reactions extending beyond the nearest joint and lasting 4 days or more had the highest recurrence rate (67%, 6/9). Patients with hypotonic hyporesponsive episodes had the lowest rate of recurrence (2%, 1/50). Allergic-like events recurred in 12% (76/659) of patients but none developed anaphylaxis. Of 33 patients with seizures following measles mumps rubella with/without varicella vaccine, none had a recurrence. Compared with patients with non-serious AEFIs, those with serious AEFIs were less often reimmunized (60% versus 80%, rate ratio: 0.8, 95% confidence interval 0.66 to 0.86).
Most patients with a history of mild or moderate AEFI can be safely reimmunized. Additional studies are needed in patients with serious AEFIs who are less likely to be reimmunized.
1 Department of social and preventive medicine, Laval University, Quebec, Canada.
2 Ministère de la santé et des services sociaux du Québec, Québec, Canada
3 CHU de Québec-Université Laval, Québec, Canada
4 Departments of pediatrics and community health & epidemiology, Dalhousie University and Canadian Center for Vaccinology, IWK Health Centre, Nova Scotia, Canada.
5 Institut National de Santé Publique du Québec, Québec, Canada.
Funding: This study was funded by the Ministère de la santé et des Services sociaux du Québec and by l’Institut national de santé publique du Québec. Zafack JG received a PhD scholarship from the Canadian Immunization Research Network (CIRN) which is sponsored by the Public Health Agency of Canada and the Canadian Institutes of Health Research.
Financial disclosure and conflict of interest: Gaston De Serres has received investigator initiated grants from GlaxoSmithKline and Pfizer. Karina Top has received in-kind research support from Pfizer and research grant from GlaxoSmithKline. Other authors have no financial relationships or conflicts of interest relevant to this article to disclose.
ACKNOWLEDGMENTS: We extend our sincere thanks to the public health unit staff across Quebec for their efforts in investigation and reporting of adverse events following immunization which are essential to the assessment of vaccine safety.
Author access to data: Zafack JG, De Serres G, Toth E and Landry M had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis
Corresponding author: Gaston De Serres, Institut national de santé publique du Québec, 2400 Avenue d’Estimauville, Quebec city, Quebec, G1E 7G9, Canada. Tel: +1-418-666-7000 x 274; fax: +1-418-666-2776; Email: firstname.lastname@example.org