Rate of Recurrence of Adverse Events Following Immunization: Results of 19 Years of Surveillance Ii Quebec, Canada
Zafack, Joseline G., MD, MPH1; Toth, Eveline, Msc2; Landry, Monique, MD2; Drolet, Jean-Philippe, MD, FRCPC3; Top, Karina A., MD, MSc4; De Serres, Gaston, MD, PhD1,3,5
The Pediatric Infectious Disease Journal: September 10, 2018 – Volume Publish Ahead of Print
Background: 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.
Methods: 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.
Results: 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).
Conclusion: 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.