The differential impact of oral poliovirus vaccine formulation choices on serotype-specific population immunity to poliovirus transmission

Abstract

BackgroundPrior analyses demonstrated the need for some countries and the Global Polio Eradication Initiative (GPEI) to conduct additional supplemental immunization activities (SIAs) with trivalent oral poliovirus vaccine (tOPV) prior to globally-coordinated cessation of all serotype 2-containing OPV (OPV2 cessation) to prevent the creation of serotype 2 circulating vaccine-derived poliovirus (cVDPV2) outbreaks after OPV2 cessation. The GPEI continues to focus on achieving and ensuring interruption of wild poliovirus serotype 1 (WPV1) and making vaccine choices that prioritize bivalent OPV (bOPV) for SIAs, nominally to increase population immunity to serotype 1, despite an aggressive timeline for OPV2 cessation.MethodsWe use an existing dynamic poliovirus transmission model of northwest Nigeria and an integrated global model for long-term poliovirus risk management to explore the impact of tOPV vs. bOPV vaccine choices on population immunity and cVDPV2 risks.ResultsUsing tOPV instead of bOPV for SIAs leads to a minimal decrease in population immunity to transmission of serotypes 1 and 3 polioviruses, but a significantly higher population immunity to transmission of serotype 2 polioviruses. Failure to use tOPV in enough SIAs results in cVDPV2 emergence after OPV2 cessation in both the northwest Nigeria model and the global model. Despite perceptions to the contrary, prioritizing the use of bOPV over tOPV prior to OPV2 cessation does not significantly improve serotype 1 population immunity to transmission.ConclusionsImmunization leaders need to focus on all three poliovirus serotypes to appropriately manage the risks of OPV cessation in the polio endgame. Focusing on population immunity to transmission to interrupt WPV1 transmission and manage pre-OPV cessation risks of cVDPVs, all countries performing poliovirus SIAs should use tOPV up until the time of OPV2 cessation, after which time they should continue to use the OPV vaccine formulation with all remaining serotypes until coordinated global cessation of those serotypes.

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

“…With the switch, the global cessation of serotype 2-containing OPV (OPV2) became a reality, and, if successful, will pave the way for the eventual cessation of the remaining two serotypes [7]. The current plan calls for simultaneous cessation of the remaining OPV serotypes (OPV13 cessation) [7], although additional delays in achieving WPV1 eradication could motivate earlier certification of WPV3 eradication and a switch from bOPV to monovalent OPV (mOPV) serotype 1 [8,9]. …”

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

“…Population immunity determines transmission, which depends on the virus finding enough unvaccinated and undervaccinated individuals to infect such that it does not die out. Recent modeling showed almost no difference in population immunity to serotype 1 transmission in northwest Nigeria after repeated bOPV rounds as compared to repeated tOPV rounds [69]. In contrast, giving bOPV and no tOPV resulted in rapidly decreasing population immunity to serotype 2 transmission and unchecked spread of cVDPV2 [69].…”

“…Recent modeling showed almost no difference in population immunity to serotype 1 transmission in northwest Nigeria after repeated bOPV rounds as compared to repeated tOPV rounds [69]. In contrast, giving bOPV and no tOPV resulted in rapidly decreasing population immunity to serotype 2 transmission and unchecked spread of cVDPV2 [69]. For any 1 SIA, only a small fraction of doses given represent first doses, and all outbreak response activities should include a minimum of 3 SIAs [62], so any focus on a single SIA misses the SIA coverage and larger population issues, which ultimately matter because transmission occurs in populations.…”

Using integrated modeling to support the global eradication of vaccine‐preventable diseases

“…• What are the impacts of various immunization options on poliovirus transmission and population immunity to poliovirus transmission in various settings of interest (Thompson et al ., , ; Kalkowska et al ., , , ; Duintjer Tebbens et al ., ; Thompson and Duintjer Tebbens, , ; Duintjer Tebbens and Thompson, )?…”

“…variability within stocks) and uncertainty about these averages. We used deterministic DEB models of poliovirus transmission (Duintjer Tebbens et al ., , ) to derive many important policy insights, including the critical importance of responding rapidly to outbreaks, even at the expense of initially lower coverage (World Health Organization, ; Thompson et al ., ), the counter‐intuitive need to intensify OPV use prior to its cessation as opposed to a gradual phase‐out (Duintjer Tebbens and Thompson, ; Kalkowska et al ., , ; Thompson and Duintjer Tebbens, ), the need to synchronize OPV cessation and verify the complete withdrawal of OPV (Duintjer Tebbens et al ., , , ), and numerous insights related to different OPV and IPV vaccination strategies to achieve and maintain eradication in specific settings (Thompson et al ., , ; Duintjer Tebbens et al ., , ; Kalkowska et al ., , , ; Thompson and Duintjer Tebbens, , ).…”