European Region successfully withdraws trivalent oral poliomyelitis (polio) vaccine
The largest ever globally coordinated switch of vaccines in routine immunization programmes took place from 17 April to 1 May 2016. This was the first step in a phased withdrawal of all oral polio vaccines (OPVs) as part of the global Polio Eradication and Endgame Strategic Plan 2013–2018.
With the switch, 19 Member States in the WHO European Region were among the 155 countries and territories across the world that stopped using trivalent OPV, which protects against all three strains of wild poliovirus. Each country either began using bivalent OPV, which provides stronger protection against the remaining two wild poliovirus strains, or switched to a schedule that includes only the inactivated form of polio vaccine (IPV). Of the 19 European Member States, 17 switched to bivalent OPV (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) and two moved to an IPV-only routine immunization schedule (Belarus and Poland). The remaining 34 Member States in the Region had already adopted an IPV-only schedule.
Health authorities in each country are expected to submit a formal report to WHO validating the successful completion of the switch. The next step will be to destroy any remaining trivalent OPV stock according to national guidance.
WHO/Europe has worked closely with countries over the past two years to ensure that all mechanisms and supplies were in place to withdraw one vaccine and introduce another in every health facility by the designated day for the switch. "The extensive preparations clearly paid off, as the process was implemented successfully in each country without any major challenges," said Dr Nedret Emiroglu, Director, Division of Communicable Diseases and Health Security. "Member States' great efforts and the strong commitment of everyone involved have contributed to a historic global public health achievement."
Rationale for the switch
While OPV is extremely safe and effective, the live attenuated polioviruses within OPV can, on very rare occasions, cause cases of circulating vaccine-derived polioviruses (cVDPVs) or vaccine-associated paralytic poliomyelitis (VAPP). Over 90% of cVDPV cases and approximately 40% of VAPP cases result from the type 2 component of trivalent OPV. This component also interferes with the immune response to poliovirus types 1 and 3. Withdrawal of the type 2 component of OPV was made possible by the worldwide eradication of this type of wild poliovirus in 1999.
To mitigate any risk associated with the withdrawal, all countries continuing to use bivalent OPV are expected to introduce at least one dose of IPV into their routine immunization programmes to maintain population immunity against the type 2 virus. A stockpile of monovalent OPV type 2 will be maintained for use in the event that any cases of cVDPV type 2 emerge after the switch. Global efforts are also under way to identify, destroy or safely contain all potentially infectious poliovirus samples in all laboratories and manufacturing sites worldwide.
One critical step closer to global polio eradication
The OPV switch represents a milestone in the comprehensive long-term strategy to achieve a polio-free world. Key lessons learnt will contribute to planning the withdrawal of all OPVs once the remaining two strains of wild poliovirus have also been eradicated. All countries and territories in the world still using OPV at that time will switch to an IPV-only routine immunization schedule.