Improving global monitoring of vaccine safety: a quantitative analysis of adverse event reports in the WHO Adverse Reactions Database

The World Health Organization (WHO) Programme for International Drug Monitoring (PIDM) was initially developed for chemical rather than biological products. The PIDM made considerable achievements in analysing drug-related adverse event reports, progress was more limited for vaccine-related reports. In 2005, the Global Advisory Committee on Vaccine Safety, called for a global consultation to address the need for improved monitoring and analysis of vaccine-related adverse event reports on an international level. In preparation for this consultation, the WHO Adverse Reactions Database was quantitatively assessed and results of this analysis are presented in this paper. Three countries contributed 82% of vaccine-related reports in the database. The mean difference between onset date and report date was 2.4 years. Several issues of concern were identified, such as the fact that many member countries do not forward any or all reports of adverse events following immunization to the PIDM, and the poor timeliness and regularity of reporting, which could prevent timely generation of safety signals.