Auzenbergs Megan, Abbas Kaja, Peak Corey M, Voorman Arend, Jit Mark, O'Reilly Kathleen M
Department of Infectious Disease Epidemiology and Dynamics, London School of Hygiene & Tropical Medicine, London, UK
Department of Infectious Disease Epidemiology and Dynamics, London School of Hygiene & Tropical Medicine, London, UK.
BMJ Glob Health. 2025 Mar 22;10(3):e016013. doi: 10.1136/bmjgh-2024-016013.
The 2021 importation of wild poliovirus serotype 1 (WPV1) into Malawi with subsequent international spread represented the first WPV1 cases in Africa since 2016. Preventing importations and spread of WPV1 is critical and dependent on population immunity provided through routine immunisation (RI) and supplementary immunisation activities (SIAs). We aim to estimate outbreak risk and costs, given the importation of WPV1 for non-endemic countries in the WHO Africa region. We developed a stochastic mathematical model of polio transmission dynamics to evaluate the probability of an outbreak, expected number of poliomyelitis cases, costs and incremental cost-effectiveness ratios under different vaccination strategies. Across variable RI coverage, we explore three key strategies: RI+outbreak SIAs (oSIAs), RI+oSIAs+annual preventative SIAs (pSIAs) and RI+oSIAs+biennial pSIAs. Results are presented in 2023 USD over a 5year- time horizon from the Global Polio Eradication Initiative (GPEI) and health system perspectives. The annual pSIA strategy has the greatest probability of no outbreaks in comparison to other strategies: under our model assumptions, annual pSIAs result in an 80% probability of no outbreaks when RI coverage is ≥50%. The biennial pSIA strategy requires RI coverage ≥65% to achieve an equivalent risk of no outbreaks. The strategy with no pSIAs requires ≥75% RI coverage to achieve an equivalent risk of no outbreaks. For the health system, when RI coverage is between 35% and 60%, both pSIA strategies are cost-saving. For the GPEI, below 65% RI pSIA strategies are cost-effective, but the biennial pSIA strategy incurs higher costs in comparison to annual pSIAs due to more oSIAs required to stop outbreaks. Prioritisation of pSIAs must balance outbreak risk against implementation costs, ideally favouring the smallest manageable outbreak risk compatible with elimination. We infer that there are few short-term risks due to population immunity from RI, but without pSIAs, long-term risks accumulate and can result in outbreaks with the potential for international spread.
2021年，野生脊髓灰质炎病毒1型（WPV1）传入马拉维并随后在国际上传播，这是自2016年以来非洲首次出现WPV1病例。预防WPV1的输入和传播至关重要，这取决于通过常规免疫（RI）和补充免疫活动（SIAs）提供的人群免疫力。我们旨在估计鉴于WPV1传入，世卫组织非洲区域非流行国家的疫情风险和成本。我们开发了一个脊髓灰质炎传播动力学的随机数学模型，以评估不同疫苗接种策略下爆发疫情的概率、脊髓灰质炎病例的预期数量、成本和增量成本效益比。在不同的RI覆盖率范围内，我们探索了三种关键策略：RI+疫情补充免疫活动（oSIAs）、RI+oSIAs+年度预防性补充免疫活动（pSIAs）和RI+oSIAs+每两年一次的pSIAs。结果以2023年美元为单位，从全球根除脊髓灰质炎倡议（GPEI）和卫生系统的角度，在5年的时间范围内呈现。与其他策略相比，年度pSIA策略无疫情爆发的概率最大：在我们的模型假设下，当RI覆盖率≥50%时，年度pSIAs导致无疫情爆发的概率为80%。每两年一次的pSIA策略要求RI覆盖率≥65%才能实现同等的无疫情爆发风险。无pSIAs策略要求RI覆盖率≥75%才能实现同等的无疫情爆发风险。对于卫生系统而言，当RI覆盖率在35%至60%之间时，两种pSIA策略都能节省成本。对于GPEI来说，RI覆盖率低于65%时，pSIA策略具有成本效益，但每两年一次的pSIA策略由于阻止疫情爆发需要更多的oSIAs，与年度pSIAs相比成本更高。优先安排pSIAs必须在疫情风险和实施成本之间取得平衡，理想情况下倾向于与消除目标相兼容的最小可管理疫情风险。我们推断，由于RI带来的人群免疫力，短期风险较小，但如果没有pSIAs，长期风险会累积，并可能导致疫情爆发并有可能在国际上传播。
