Global patterns and trends in spontaneous reporting systems: VigiBase, FAERS, VAERS, and JADER.

INTRODUCTION: Spontaneous reporting systems (SRSs) gather millions of reports of adverse events occurring to patients worldwide. For its volume and breadth of data, they are often regarded as the cornerstone of pharmacovigilance. However, their individual and intra-database characteristics remain incompletely described. METHODS: Four SRSs were considered, namely, the WHO global database VigiBase, the FDA Adverse Event Reporting System (FAERS), the Vaccine Adverse Event Reporting System (VAERS), and the Japanese Adverse Drug Event Report database (JADER). As of 31 December 2025, these databases contain approximately 42.4 million, 26.3 million, 2.7 million and 0.9 million reports, respectively. Following deduplication, approximately 11.1 million reports were uniquely shared between VigiBase and FAERS and close to 1.3 million between VigiBase and VAERS. RESULTS: We described and compared report features such as drug and adverse event reporting patterns, reporter types, geographic distribution, demographics, and medical outcomes. Most reports have been received in recent years across the four databases with up to 70% of the reports accumulated in the last 7-14 years, depending on the SRS. Notable patterns appeared in reporter types (consumer-dominated in FAERS versus physician-dominated in JADER), sex (female predominance in VigiBase, FAERS and VAERS, versus near-parity in JADER), and the influence of COVID-19 vaccination campaigns, which disproportionately affected VigiBase and VAERS. Time-series trends were analysed by comparing reports pre and post 1 January 2015, excluding COVID-19 vaccine reports. Changes in reporting patterns of therapeutic subgroups and adverse events since 2015 were consistent across SRSs with some region-specific variations. DISCUSSION: By highlighting differences between SRSs, this manuscript serves as a reference for researchers and regulators.