Preparation for global introduction of inactivated poliovirus vaccine: safety evidence from the US Vaccine Adverse Event Reporting System, 2000-12

Abstract

Background: Safety data from countries with experience in the use of inactivated poliovirus vaccine (IPV) are important for the global polio eradication strategy to introduce IPV into the immunisation schedules of all countries. In the USA, IPV has been included in the routine immunisation schedule since 1997. We aimed to analyse adverse events after IPV administration reported to the US Vaccine Adverse Event Reporting System (VAERS).

Methods: We analysed all VAERS data associated with IPV submitted between Jan 1, 2000, and Dec 31, 2012, either as individual or as combination vaccines, for all age and sex groups. We analysed the number and event type (non-serious, non-fatal serious, and death reports) of individual reports, and explored the most commonly coded event terms to describe the adverse event. We classified death reports according to previously published body-system categories (respiratory, cardiovascular, neurological, gastrointestinal, other infectious, and other non-infectious) and reviewed death reports to identify the cause of death. We classified sudden infant death syndrome as a separate cause of death considering previous concerns about sudden infant syndrome after vaccines. We used empirical Bayesian data mining methods to identify disproportionate reporting of adverse events for IPV compared with other vaccines. Additional VAERS data from 1991 to 2000 were analysed to compare the safety profiles of IPV and oral poliovirus vaccine (OPV).

Findings: Of the 41,792 adverse event reports submitted, 39,568 (95%) were for children younger than 7 years. 38,381 of the reports for children in this age group (97%) were for simultaneous vaccination with IPV and other vaccines (most commonly pneumococcal and acellular pertussis vaccines), whereas standalone IPV vaccines accounted for 0·5% of all reports. 34,880 reports were for non-serious events (88%), 3905 reports were for non-fatal serious events (10%), and 783 reports were death reports (2%). Injection-site erythema was the most commonly coded term for non-serious events (29%), and pyrexia for non-fatal serious events (38%). Most deaths (96%) were in children aged 12 months or younger; most (52%) had sudden infant death syndrome as the reported cause of death. The safely profiles of combined IPV and whole-cell pertussis vaccines, OPV and whole-cell pertussis vaccines, and OPV and acellular pertussis vaccines were similar. We noted no indication of disproportionate reporting of adverse events after immunisation with IPV-containing vaccines compared with other vaccines between 1990 and 2013.

Interpretation: Fairly few adverse events were reported for the more than 250 million IPV doses distributed between 2000 and 2012. Sudden infant death syndrome reports after IPV were consistent with reporting patterns for other vaccines. No new or unexpected vaccine safety problems were identified for fatal, non-fatal serious, and non-serious reports in this assessment of adverse events after IPV.

Funding: None.