Applicability of the Brighton Collaboration Case Definition for seizure after immunization in active and passive surveillance in Canada

Background: The Canadian Adverse Event Following Immunization Surveillance System (CAEFISS) receives reports via active syndromic surveillance for selected serious AEFI from the Canadian Immunization Monitoring Program Active (IMPACT) and via targeted passive surveillance from Federal/Provincial/Territorial health jurisdictions. Post-immunization seizure is a target of active and passive surveillance. Since 2009, the revised national AEFI reporting forms enable capture of terms specific to several Brighton Collaboration Case Definitions (BCCD) including generalized seizure and fever. Objective: To evaluate feasibility of applying the BCCD for generalized seizure to adverse event following immunization (AEFI) reports collected by IMPACT and targeted passive surveillance (non-IMPACT). Methods: Reports to CAEFISS coded as seizure in children <2 years of age (vaccination dates 1998-2011) were reviewed retrospectively. A BCCD level (1-5 or unclassifiable) was assigned. The effects of reporting source (IMPACT versus non-IMPACT), seriousness [serious (e.g., hospitalized) versus non-serious], vaccination year (1998-2008 versus 2009-2011), and data submission method to CAEFISS (electronic versus paper) were assessed by stratified analysis. Results: There were 459 IMPACT and 908 non-IMPACT cases analyzed, of which 99.6% and 27%, respectively, were serious reports. The revised reporting form that captured the BCCD components (2009-2011) was associated with increased proportions of IMPACT and non-IMPACT cases meeting the BCCD for generalized seizure. Conclusions: Incorporating the BCCD components (level of consciousness, motor manifestations and fever ≥38. °C) into the national reporting form and guidelines appeared to improve the feasibility of their use in AEFI surveillance. This effect was more pronounced among active syndromic surveillance compared to targeted passive surveillance reports.