<< Back To Home

Cessation of use of trivalent oral polio vaccine and introduction of inactivated poliovirus vaccine worldwide

Friday, 23rd of September 2016 Print

Weekly epidemiological record

9 SEPTEMBER 2016, 91th YEAR, 36/37, 2016, 91, 421–432

http://www.who.int/wer 2016, 91, 421-432

Cessation of use of trivalent oral polio vaccine and introduction of inactivated poliovirus vaccine worldwide

Excerpt below; full text is at http://apps.who.int/iris/bitstream/10665/250045/1/WER9136_37.pdf

Since the 1988 World Health Assembly resolution to eradicate poliomyelitis, transmission of the 3 types of wild poliovirus (WPV) has been greatly reduced.1 WPV type 2 (WPV2) has not been detected since 1999 and was declared eradicated in September 2015. Given that WPV type 3 has not been detected since November 2012, WPV type 1 (WPV1) is likely to be the sole WPV remaining in circulation. This marked progress has been achieved through widespread use of oral poliovirus vaccines (OPVs), most commonly trivalent OPV (tOPV), which contains types 1, 2 and 3 live, attenuated polioviruses, and has been a mainstay of efforts to prevent polio since the early 1960s. Attenuated polioviruses in OPV can undergo genetic changes during replication, and in communities with low vaccination coverage rarely result in vaccine-derived polioviruses (VDPVs) that can cause paralytic polio indistinguishable from the disease caused by WPVs.2 Among the 721 polio cases caused by circulating VDPVs (cVDPVs) detected between January 2006 and May 2016, type 2 cVDPVs (cVDPV2s) accounted for >94%.2 Eliminating the risk of polio caused by VDPVs requires the stopping of all OPV use. The first stage of OPV withdrawal involved a global, synchronized cessation of tOPV use planned for 18 April–1 May 2016, replacing tOPV with bivalent OPV (bOPV) containing only types 1 and 3 polioviruses, and withdrawing OPV type 2 from all immunization activities.3

Complementing the switch from tOPV to bOPV was the introduction of at least one dose of injectable, trivalent inactivated poliovirus vaccine (IPV) into childhood immunization schedules which reduces the risks from, and facilitates responses to, cVDPV2 outbreaks. This report summarizes global progress in the cessation of tOPV use and the introduction of IPV.

All 155 countries and territories that were continuing use of OPV in immunization schedules in 2015 reported that they had ceased use of tOPV by mid-May 2016. As of 31 August 2016, 173 (89%) of 194 WHO Member States included IPV in their immunization schedules. The cessation of tOPV use is a significant step in completing the global effort to eradicate polio; however, careful surveillance for polioviruses and prompt, aggressive responses to outbreaks are still needed to create a world free from the disease. Global cessation of use of trivalent OPV Although the global cessation of tOPV use is essential for eliminating cVDPV2s, it carries some risks in facilitating the spread of undetected or newly emergent cVDPV2s among persons without immunity to type 2 poliovirus infections after the switch.4, 5

To stop the spread of existing cVDPV2s before the switch and to reduce risks for post-switch outbreaks, population immunity to type 2 poliovirus at the time of the switch was boosted through implementation of at least 116 supplementary immunization activities (SIAs) with tOPV in 42 OPV-using countries during November 2015–April 2016. Afghanistan, Nigeria and Pakistan conducted SIAs with IPV in selected regions before ceasing tOPV use. In addition, the synchronized timing of the switch aimed to prevent exportations of type 2 polioviruses from areas continuing to use tOPV to neighbouring areas that had ceased tOPV use.3, 4 All 155 countries and territories using OPV in 2015 reported cessation of use of tOPV by 12 May 2016 (Map 1).6 To facilitate the global cessation of tOPV use, all manufacturers of OPV ceased production of tOPV before the switch and after several years of communication and close coordination with the Global Polio Eradication Initiative (GPEI).

 

40761448