■脊髓灰质炎病毒传播的检测和正在进行的口服脊髓灰质炎疫苗(OPV)的使用继续延迟脊髓灰质炎的根除。2016年,全球根除脊髓灰质炎倡议(GPEI)协调全球停止2型OPV(OPV2)用于预防性免疫,并将其用于紧急疫情应对。2019年,GPEI合作伙伴要求重启一些SabinOPV2的生产,并加快了转基因新型OPV2疫苗(nOPV2)的开发,该疫苗承诺比单价SabinOPV2(mOPV2)具有更大的遗传稳定性。
■我们回顾了综合风险,经济,以及在OPV2停止之前进行的全球脊髓灰质炎病毒传播建模,建议采用多种风险管理策略,以增加成功终止2型脊髓灰质炎病毒所有传播的机会。OPV2停止后,各国实施的战略和GPEI偏离了模型推荐的风险管理战略。补充其他模型,探索前瞻性爆发反应选项,以改善当前脊髓灰质炎结局轨迹的结果,在这项研究中,我们将时间倒退到2017年,并探讨了如果GPEI有以下情况,脊髓灰质炎终局可能遵循的反事实轨迹:(1)在OPV2停止后对风险的管理不同,和/或(2)之前开发了nOPV2,并将其专门用于OPV2停止后的爆发反应.
■2016年基于模型的推荐疫情应对策略的实施可能已经结束(并且仍然可以大大提高结束2型脊髓灰质炎病毒传播的可能性)。自2016年以来观察到的疫情应对表现预计不会以高信心实现OPV2停止,即使在2016年OPV2停止之前有NOPV2。
■实施时,2016年停止OPV2未能停止2型传输.虽然nOPV2具有较低的额外爆发风险的好处,其相对于mOPV2的二次传播减少可能意味着nOPV2比mOPV2需要相对更高的覆盖率以阻止暴发.
Detection of poliovirus transmission and ongoing oral poliovirus vaccine (OPV) use continue to delay poliomyelitis eradication. In 2016, the Global Polio Eradication Initiative (GPEI) coordinated global cessation of type 2 OPV (OPV2) for preventive immunization and limited its use to emergency outbreak response. In 2019, GPEI partners requested restart of some Sabin OPV2 production and also accelerated the development of a genetically modified novel OPV2 vaccine (nOPV2) that promised greater genetic stability than monovalent Sabin OPV2 (mOPV2).
We reviewed integrated risk, economic, and global poliovirus transmission modeling performed before OPV2 cessation, which recommended multiple risk management strategies to increase the chances of successfully ending all transmission of type 2 live polioviruses. Following OPV2 cessation, strategies implemented by countries and the GPEI deviated from model recommended risk management strategies. Complementing other modeling that explores prospective outbreak response options for improving outcomes for the current polio endgame trajectory, in this study we roll back the clock to 2017 and explore counterfactual trajectories that the polio endgame could have followed if GPEI had: (1) managed risks differently after OPV2 cessation and/or (2) developed nOPV2 before and used it exclusively for outbreak response after OPV2 cessation.
The implementation of the 2016 model-based recommended outbreak response strategies could have ended (and could still substantially improve the probability of ending) type 2 poliovirus transmission. Outbreak response performance observed since 2016 would not have been expected to achieve OPV2 cessation with high confidence, even with the availability of nOPV2 prior to the 2016 OPV2 cessation.
As implemented, the 2016 OPV2 cessation failed to stop type 2 transmission. While nOPV2 offers benefits of lower risk of seeding additional outbreaks, its reduced secondary spread relative to mOPV2 may imply relatively higher coverage needed for nOPV2 than mOPV2 to stop outbreaks.