Medical Research Council Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, UK.
Bill & Melinda Gates Foundation, Seattle, WA, USA.
Lancet Infect Dis. 2022 Feb;22(2):284-294. doi: 10.1016/S1473-3099(21)00453-9. Epub 2021 Oct 11.
Expanding outbreaks of circulating vaccine-derived type 2 poliovirus (cVDPV2) across Africa after the global withdrawal of trivalent oral poliovirus vaccine (OPV) in 2016 are delaying global polio eradication. We aimed to assess the effect of outbreak response campaigns with monovalent type 2 OPV (mOPV2) and the addition of inactivated poliovirus vaccine (IPV) to routine immunisation.
We used vaccination history data from children under 5 years old with non-polio acute flaccid paralysis from a routine surveillance database (the Polio Information System) and setting-specific OPV immunogenicity data from the literature to estimate OPV-induced and IPV-induced population immunity against type 2 poliomyelitis between Jan 1, 2015, and June 30, 2020, for 51 countries in Africa. We investigated risk factors for reported cVDPV2 poliomyelitis including population immunity, outbreak response activities, and correlates of poliovirus transmission using logistic regression. We used the model to estimate cVDPV2 risk for each 6-month period between Jan 1, 2016, and June 30, 2020, with different numbers of mOPV2 campaigns and compared the timing and location of actual mOPV2 campaigns and the number of mOPV2 campaigns required to reduce cVDPV2 risk to low levels.
Type 2 OPV immunity among children under 5 years declined from a median of 87% (IQR 81-93) in January-June, 2016 to 14% (9-37) in January-June, 2020. Type 2 immunity from IPV among children under 5 years increased from 3% (<1-6%) in January-June, 2016 to 35% (24-47) in January-June, 2020. The probability of cVDPV2 poliomyelitis among children under 5 years was negatively correlated with OPV-induced and IPV-induced immunity and mOPV2 campaigns (adjusted odds ratio: OPV 0·68 [95% CrI 0·60-0·76], IPV 0·82 [0·68-0·99] per 10% absolute increase in estimated population immunity, mOPV2 0·30 [0·20-0·44] per campaign). Vaccination campaigns in response to cVDPV2 outbreaks have been smaller and slower than our model shows would be necessary to reduce risk to low levels, covering only 11% of children under 5 years who are predicted to be at risk within 6 months and only 56% within 12 months.
Our findings suggest that as mucosal immunity declines, larger or faster responses with vaccination campaigns using type 2-containing OPV will be required to stop cVDPV2 transmission. IPV-induced immunity also has an important role in reducing the burden of cVDPV2 poliomyelitis in Africa.
Bill & Melinda Gates Foundation, Medical Research Council Centre for Global Infectious Disease Analysis, and WHO.
For the French translation of the abstract see Supplementary Materials section.
2016 年全球停用三价口服脊髓灰质炎疫苗（tOPV）后，非洲循环疫苗衍生 2 型脊髓灰质炎病毒（cVDPV2）的爆发不断扩大，这使得全球根除脊髓灰质炎工作受阻。本研究旨在评估使用单价 2 型口服脊髓灰质炎疫苗（mOPV2）开展疫情应对活动，以及在常规免疫中加入脊灰灭活疫苗（IPV）的效果。
我们使用来自常规监测数据库（脊髓灰质炎信息系统）的 5 岁以下儿童非脊灰急性弛缓性麻痹病例的疫苗接种史数据和文献中特定地点的 tOPV 免疫原性数据，估计 2015 年 1 月 1 日至 2020 年 6 月 30 日期间，51 个非洲国家中 OPV 诱导和 IPV 诱导的 2 型脊髓灰质炎人群免疫力。我们使用逻辑回归调查了报告的 cVDPV2 脊髓灰质炎的风险因素，包括人群免疫力、疫情应对活动以及与病毒传播相关的因素。我们使用该模型估计 2016 年 1 月 1 日至 2020 年 6 月 30 日期间每 6 个月的 cVDPV2 风险，并比较了实际 mOPV2 疫苗接种活动的时间和地点，以及需要开展多少次 mOPV2 疫苗接种活动，才能将 cVDPV2 风险降低到低水平。
2016 年 1 月至 6 月期间，5 岁以下儿童 2 型 OPV 免疫力中位数从 87%（81-93）降至 2020 年 1 月至 6 月的 14%（9-37）。2016 年 1 月至 6 月期间，5 岁以下儿童 IPV 诱导的 2 型免疫力从 3%（<1-6%）增至 2020 年 1 月至 6 月的 35%（24-47）。5 岁以下儿童发生 cVDPV2 脊髓灰质炎的概率与 OPV 诱导和 IPV 诱导的免疫力以及 mOPV2 疫苗接种活动呈负相关（调整后的优势比：OPV 每增加 10%估计的人群免疫力为 0.68[95%CI 0.60-0.76]，IPV 为 0.82[0.68-0.99]；mOPV2 为 0.30[0.20-0.44]）。应对 cVDPV2 疫情的疫苗接种活动规模较小且进展较慢，这与我们的模型显示的降低风险至低水平所需的活动规模不符，这些活动仅覆盖了预测在 6 个月内处于风险中的 5 岁以下儿童的 11%，在 12 个月内仅覆盖了 56%。
我们的研究结果表明，随着黏膜免疫力下降，需要开展更大规模或更快速的疫苗接种活动，包括使用含 2 型病毒的 OPV，以阻止 cVDPV2 的传播。IPV 诱导的免疫力也在降低非洲 cVDPV2 脊髓灰质炎负担方面发挥着重要作用。
比尔及梅琳达·盖茨基金会、医学研究理事会全球传染病分析中心和世卫组织。
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