Withdrawal of trivalent oral polio vaccine in the European Region (OPV switch)
There are three serotypes of wild poliovirus – type 1, type 2, and type 3. One of these, type 2 wild poliovirus (WPV2), was declared officially eradicated in September 2015 by the Global Commission for the Certification of Poliomyelitis Eradication (GCC), as no cases of this serotype had been detected globally since October 1999.
All oral polio vaccines (OPV) are made from live attenuated (weakened) polioviruses. Due to natural evolution in one (or several) human beings, these viruses can in very rare cases mutate into vaccine-derived poliovirus (VDPV) and acquire the capacity for long-term circulation that can even lead to polio outbreaks, especially in areas of low vaccination coverage.
As planned in the Polio Eradication and Endgame Strategic Plan 2013–2018, gradual cessation of the use of all OPVs began in 2016 with withdrawal of the type 2 component (OPV2). The choice to withdraw OPV2 was based on the following considerations:
- Wild poliovirus type 2 is no longer circulating anywhere in the world.
- OPV2 interferes with the immune response to poliovirus types 1 and 3; therefore its withdrawal from the vaccine increases the effectiveness of immunization against polioviruses of other serotypes.
All immunization programmes in the world that use OPV were required to switch from trivalent OPV (containing all 3 poliovirus types) to bivalent OPV (containing only types 1 and 3), or move to an inactivated polio vaccine (IPV)-only schedule, in a globally synchronized manner between 17 April and 1 May 2016. In addition, at least one dose of IPV is being added to the routine immunization schedule in each country that uses bivalent OPV to boost protection against all three types of poliovirus.
In conjunction with the switch, any remaining trivalent OPV stock had to be collected and destroyed according to national guidance.
OPV switch in the European Region
19 Member States in the WHO European Region used trivalent OPV in their routine immunization schedules before the switch, in some cases already in combination with IPV.
Albania, Armenia, Azerbaijan, Bosnia and Herzegovina, Georgia, Kazakhstan, Kyrgyzstan, Montenegro, the Republic of Moldova, the Russian Federation, Serbia, Tajikistan, the former Yugoslav Republic of Macedonia, Turkey, Turkmenistan, Ukraine and Uzbekistan switched from trivalent to bivalent OPV. Belarus and Poland moved to an IPV-only schedule.
Throughout the world, this switch was preceded by initial steps to ensure global containment of all infectious and potentially infectious type 2 poliovirus materials in laboratory and vaccine production facilities.
