Risk of Recurrence of Adverse Events Following Immunization: A Systematic Review.

CONTEXT: Reimmunizing patients who had an adverse event following immunization (AEFI) is sometimes a challenge because there are limited data on the risk and severity of AEFI recurrence. OBJECTIVE: To summarize the literature on the risk of AEFI recurrence. DATA SOURCES: PubMed, Embase, and Cochrane library. STUDY SELECTION: We included articles in English or French published before September 30, 2016. Articles were selected if they estimated the risk of AEFI recurrence in at least 5 individuals. Studies with experimental vaccines were excluded. DATA EXTRACTION: Data on study design, setting, population, vaccines, and AEFI recurrence were extracted. RESULTS: Twenty-nine articles were included. Among patients with a history of hypotonic hyporesponsive episode (n = 398), anaphylaxis (n = 133), or seizures (n = 60) who were reimmunized, events recurred in 0% to 0.8%. Allergic-like events recurred in 30 of 594 reimmunized patients. Fever recurred in 0% to 84% of 836 reimmunized patients, depending on the vaccine and dose number. Among children with extensive limb swelling after the fourth dose of diphtheria-tetanus-acellular pertussis vaccine, recurrence was higher when the fifth dose was given withthe full-antigen formulation (78%) compared with the reduced-antigen formulation (53%, P = .02) LIMITATIONS: Many studies, included few patients, and those with severe AEFIs were often not reimmunized. CONCLUSIONS: Despite vaccines being administered to millions of people annually, there are few studies in which researchers evaluated AEFI recurrence. Published studies suggest that reimmunization is usually safe. However in these studies, severe cases were often not reimmunized.