OPV Cessation
Why OPV cessation?
Oral polio vaccine (OPV) is extremely safe and effective at protecting children against lifelong polio paralysis. Over the past ten years, more than 20 billion doses of OPV have been given to nearly three billion children worldwide. More than 20 million cases of polio have been prevented, and the disease has been reduced by more than 99%.
OPV contains attenuated (weakened) polioviruses. On extremely rare occasions, use of OPV can result in cases of polio due to vaccine-associated paralytic polio (VAPP) and circulating vaccine-derived polioviruses (cVDPVs). For this reason, the global eradication of polio requires the cessation of all OPV in routine immunization, as soon as possible after the eradication of wild poliovirus (WPV) transmission.
Phased approach to OPV cessation – trivalent OPV to bivalent OPV switch
Historically, OPV has been available in different formulations:
- Trivalent OPV – containing type 1, 2 and 3 serotypes
- Bivalent OPV – containing type 1 and 3 serotypes
- Monovalent OPV – containing one serotype (ie type 1, 2 or 3)
A mix of all three formulations was being used to eradicate polio during supplementary immunization activities (SIAs). However, only trivalent OPV was used in routine immunization programmes. Bivalent OPV was exclusively used during SIAs to more rapidly interrupt the transmission of WPV1 and 3 – the only remaining WPV strains in circulation. WPV2 has been eradicated since 1999.
With the transmission of WPV2 already successfully interrupted, the only cases of type 2 paralytic polio were being caused by the type 2 serotype component in trivalent OPV. Over 90% of cVDPV cases were due to the type 2 component, which was also responsible for up to 38% of VAPP cases (approx. 200 cases per year worldwide).
The switch
In April 2016 a switch was implemented from trivalent OPV to bivalent OPV in routine immunization programmes.
Following WPV1 and WPV3 eradication, use of all OPV in routine immunizations will be stopped.
Switch lessons learned project – draft for public consultation
The Strategy Committee of the Global Polio Eradication Initiative (GPEI) in 2023 commissioned an external evaluation of the 2016 global withdrawal of Sabin poliovirus 2 (OPV2) and switch from trivalent oral polio vaccine (tOPV) to bivalent OPV (bOPV). The evaluation aims to generate critical lessons learnt from the OPV2 withdrawal, in order to guide the direction of the GPEI (including future OPV withdrawal efforts) and secure a lasting world free of all polioviruses. The evaluation was designed and implemented by a team of experts, informed by a wide range of stakeholder consultations across all levels, and presented last month to the Strategic Advisory Group of Experts on immunization (SAGE). To ensure the evaluation is as relevant and useful as possible, and to provide the public health community and other interested stakeholders the opportunity to contribute, the lessons learned team is soliciting thoughts, comments and suggestions on the public draft for consultation. Interested stakeholders and members of the public health community are invited to share any contributions, ideas or suggestions by Friday 10 May 2024, to: Switch@who.int. Final publication of the evaluation on www.polioeradication.org is anticipated shortly after this public consultation.
