The impact of regulation changes in the spontaneous reporting system for vaccines on reporting trends and signal detection in Japan

Purpose: Spontaneous reporting constitutes one of the most fundamental and important systems for pharmacovigilance. In Japan, important regulation changes in the vaccine spontaneous reporting were implemented between 2009 and 2013; however, no studies had yet assessed the impact of the changes. The objective of this study was to assess the impact on the reporting trends in vaccine reports and on signal detection for vaccines. Methods: For assessment of the impact on the reporting trends, we performed the joinpoint trend analysis and descriptively considered number of vaccine reports grouped by the timing of the regulation change. For assessment of the impact on signal detection, we performed signal detection using dataset during the pre or postperiod of the regulation changes, and compared their agreement rates, which was calculated with a reference set for vaccines, created by the Global Research in Paediatrics project. Results: We retrieved 467 635 spontaneous reports, including 12 287 vaccine reports from April 2004 to March 2019. The average number of vaccine reports per year increased from 231 reports during the preperiod to 1227 during the postperiod. The joinpoint trend analysis found two joinpoints and differentiated three trends, significant increased trend of which was observed when regulations had changed. For signal detection, the agreement rate was improved when using data during the postperiod. Conclusion: We concluded that the regulation changes increased the number of vaccine reports, and could have improved signal detection performance for vaccines by accelerating accumulation of reports, while more spontaneous reports are necessary to optimize signal detection.