Vaccine-Associated Paralytic Poliomyelitis - 8 PLADs, China, October 2012-March 2014.

Introduction: Poliomyelitis is a highly contagious, seasonal viral disease caused by any of three poliovirus (PV) serotypes (types 1, 2, or 3). Oral poliovirus vaccine (OPV) on rare occasions causes vaccine-associated paralytic poliomyelitis (VAPP) in recipients of OPV and close contacts of recently vaccinated individuals. This study describes the epidemiology of VAPP when an all OPV schedule was used in the Expanded Program on Immunization (EPI). Methods: VAPP cases were identified using standardized diagnostic criteria from data reported by 8 provincial-level administrative divisions (PLADs) to the National Acute Flaccid Paralysis (AFP) Surveillance System in an 18-month period between October 2012 and March 2014. Results: During this period, 28 VAPP cases were reported. Using the number of births as a denominator, the estimated incidence of VAPP was 2.47 cases per million births. Using the number of OPV doses administered through routine immunization, the VAPP incidence was 0.55 cases per million doses. Among vaccine-recipient VAPP cases, 22 (85%) were associated with the first dose of OPV; 3 were associated with the second OPV dose. The relative risk of VAPP following the first dose compared with the second dose was 7.07. Conclusions and Implications for Public Health Practice: The per-dose and per-child incidences of VAPP were consistent with incidence estimates by the World Health Organization (WHO). The vast majority (85%) of VAPP in China was associated with the first dose of OPV in an all-OPV schedule. Because inactivated polio vaccine (IPV) is known to prevent VAPP from subsequent doses of OPV in immunocompetent children, this association provided strong evidence for using an IPV-first, sequential IPV-OPV polio vaccination schedule in China during the globally-synchronized cessation of type 2 OPV and introduction of IPV in 2016.