Maintenance and Intensification of Bivalent Oral Poliovirus Vaccine Use Prior to its Coordinated Global Cessation

Background.Comparing model expectations with the experience of oral poliovirus vaccine (OPV) containing serotype 2 (OPV2) cessation can inform risk management for the expected cessation of OPV containing serotypes 1 and 3 (OPV13). Methods.We compare the expected post-OPV2-cessation OPV2-related viruses from models with the evidence available approximately 6 months after OPV2 cessation. We also model the trade-offs of use vs nonuse of monovalent OPV (mOPV) for outbreak response considering all 3 serotypes.Results.Although too early to tell definitively, the observed die-out of OPV2-related viruses in populations that attained sufficiently intense trivalent OPV (tOPV) use prior to OPV2 cessation appears consistent with model expectations. As expected, populations that did not intensify tOPV use prior to OPV2 cessation show continued circulation of serotype 2 vaccine-derived polioviruses (VDPVs). Failure to aggressively use mOPV to respond to circulating VDPVs results in a high risk of uncontrolled outbreaks that would require restarting OPV.Conclusions.Ensuring a successful endgame requires more aggressive OPV cessation risk management than has occurred to date for OPV2 cessation. This includes maintaining high population immunity to transmission up until OPV13 cessation, meeting all prerequisites for OPV cessation, and ensuring sufficient vaccine supply to prevent and respond to outbreaks.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Lessons From Globally Coordinated Cessation of Serotype 2 Oral Poliovirus Vaccine for the Remaining Serotypes

Thompson

Tebbens²

2017

“…Given that Nigeria historically exported WPV1 to numerous countries in Africa and elsewhere that did not maintain sufficient population immunity to poliovirus transmission [48], countries with poor RI coverage remain at risk. These countries need to continue to conduct preventive SIAs, using bOPV, to keep their population immunity to transmission high and prevent any importations of the circulating WPV1 from restarting transmission and causing new outbreaks within their borders [49]. The increased use of inactivated poliovirus vaccine (IPV), which results in a weaker immune response at the individual level and leads to relatively lower population immunity to transmission than OPV, will not play an important role in preventing cVDPVs in OPV-using countries prior to bOPV cessation [50], substantially accelerate eradication in polio-endemic countries [36][37][38], or represent a cost-effective option when used in addition to OPV in outbreak response [51].…”

Section: Resultsmentioning

confidence: 99%

Lessons From the Polio Endgame: Overcoming the Failure to Vaccinate and the Role of Subpopulations in Maintaining Transmission

Thompson

Tebbens²

2017

Background.Recent detections of circulating serotype 2 vaccine-derived poliovirus in northern Nigeria (Borno and Sokoto states) and Pakistan (Balochistan Province) and serotype 1 wild poliovirus in Pakistan, Afghanistan, and Nigeria (Borno) represent public health emergencies that require aggressive response.Methods.We demonstrate the importance of undervaccinated subpopulations, using an existing dynamic poliovirus transmission and oral poliovirus vaccine evolution model. We review the lessons learned during the polio endgame about the role of subpopulations in sustaining transmission, and we explore the implications of subpopulations for other vaccine-preventable disease eradication efforts.Results.Relatively isolated subpopulations benefit little from high surrounding population immunity to transmission and will sustain transmission as long as they do not attain high vaccination coverage. Failing to reach such subpopulations with high coverage represents the root cause of polio eradication delays. Achieving and maintaining eradication requires addressing the weakest links, which includes immunizing populations in insecure areas and/or with disrupted or poor-performing health systems and managing the risks of individuals with primary immunodeficiencies who can excrete vaccine-derived poliovirus long-term.Conclusions.Eradication efforts for vaccine-preventable diseases need to create performance expectations for countries to immunize all people living within their borders and maintain high coverage with appropriate interventions.Keywords. Polio; eradication; transmission; heterogeneity.

“…Among countries and territories procuring bOPV through UNICEF, SIAs are the key demand driver, with routine immunization accounting for approximately 20% of UNICEF’s procurement of 1.2 billion doses in 2016. Similar to tOPV withdrawal, successful withdrawal of bOPV will depend on finding a balance between the scaling back of production by global and domestic manufacturers and ensuring sufficient availability of types 1 and 3 bulk and finished bOPV to meet routine immunization, outbreak response, and planned SIA demand through the date of OPV withdrawal [ 13 ]. Factors that can facilitate a favorable balance include advanced notification of the date of withdrawal to manufacturers and countries, inventories of countries’ OPV stocks, and accurate country and global quantification of demand for bOPV.…”

Section: Manufacturing and Distribution Of Bivalent Opvmentioning

confidence: 99%

Considerations for the Full Global Withdrawal of Oral Polio Vaccine After Eradication of Polio

Hampton

Châtellier

Fournier-Caruana

et al. 2017

Eliminating the risk of polio from vaccine-derived polioviruses is essential for creating a polio-free world, and eliminating that risk will require stopping use of all oral polio vaccines (OPVs) once all types of wild polioviruses have been eradicated. In many ways, the experience with the global switch from trivalent OPV (tOPV) to bivalent OPV (bOPV) can inform the eventual full global withdrawal of OPV. Significant preparation will be needed for a thorough, synchronized, and full withdrawal of OPV, and such preparation would be aided by setting a reasonably firm date for OPV withdrawal as far in advance as possible, ideally at least 24 months. A shorter lead time would provide valuable flexibility for decisions about when to stop use of OPV in the context of uncertainty about whether or not all types of wild polioviruses had been eradicated, but it might increase the cost of OPV withdrawal.