Behind the scenes in public health: Adverse events following immunization (AEFI) signal investigation in British Columbia

Abstract

Background In British Columbia, vaccine safety is monitored through a passive surveillance system with voluntary reporting of adverse events following immunization (AEFIs) from immunizers to five regional health authorities and onward to the British Columbia Centre for Disease Control (BCCDC). Objective To review and summarize all documented AEFI cluster or signal investigations carried out by BCCDC between November 2007 and July 2014. Method Documented cluster or signal investigations were reviewed to summarize year, alerting mechanism, event type and vaccine, investigative analysis approach, results, and public health actions. The findings and public health actions of two cluster investigations are described in detail. Results There were two fatality investigations and thirteen cluster investigations. The two fatalities were found to be due to sudden infant death syndrome and were not vaccine-related. Clusters were predominantly identified through notification from regional medical health officers or public health nurses, and the majority were local injection site reactions (54%), or allergic events (39%). Most investigations did not identify a specific association to a vaccine or a lot of vaccine, and no public health actions were taken. Two recent investigations-reports of hypotonic-hyporesponsive episodes with or without severe vomiting and diarrhea following receipt of a single lot of DPT-IPV/Hib/hepatitis B vaccine, and reports of severe pain past nearest joint following administration of a single lot of influenza vaccine-were thought to be vaccine-related. The former investigation did not find an association to vaccine, while the severe local reactions post-influenza immunization were determined to be a result of improper injection technique. Public health actions included communication to federal/provincial/territorial vaccine safety partners and additional injection technique training. Conclusion This investigative aspect of public health immunization programs is often not in the public eye but is an important component of behind the scenes activities that serve to protect public safety.