A public health catch-22 In 2016, the serotype 2 component of the oral poliovirus vaccine given to children was withdrawn. This measure was taken to prevent vaccine-associated disease outbreaks caused by mutation in the live attenuated vaccine. Children around the world now have poor immunity to serotype 2 poliovirus because the inactivated vaccine is far less effective and a new oral vaccine is not yet ready. Using a statistical model, Macklin et al. discovered that most current outbreaks of polio in several countries across Asia and sub-Saharan Africa are likely associated with the serotype 2 vaccine strain (see the Perspective by Donlan and Petri). To block transmission when poliovirus outbreaks occur requires deployment of the only tool in the box: the existing live attenuated serotype 2 oral vaccine, which increases the risk of vaccine-derived disease. Science, this issue p. 401; see also p. 362 Outbreaks of serotype 2 vaccine-derived poliovirus can be traced to use of the oral poliovirus vaccine in outbreak response campaigns. Although there have been no cases of serotype 2 wild poliovirus for more than 20 years, transmission of serotype 2 vaccine-derived poliovirus (VDPV2) and associated paralytic cases in several continents represent a threat to eradication. The withdrawal of the serotype 2 component of oral poliovirus vaccine (OPV2) was implemented in April 2016 to stop VDPV2 emergence and secure eradication of all serotype 2 poliovirus. Globally, children born after this date have limited immunity to prevent transmission. Using a statistical model, we estimated the emergence date and source of VDPV2s detected between May 2016 and November 2019. Outbreak response campaigns with monovalent OPV2 are the only available method to induce immunity to prevent transmission. Yet our analysis shows that using monovalent OPV2 is generating more paralytic VDPV2 outbreaks with the potential for establishing endemic transmission. A novel OPV2, for which two candidates are currently in clinical trials, is urgently required, together with a contingency strategy if this vaccine does not materialize or perform as anticipated.

中文翻译：

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2 型口服脊髓灰质炎病毒疫苗停用后 2 型脊髓灰质炎病毒流行病学的演变


公共卫生的第 22 条军规 2016 年，儿童口服脊髓灰质炎病毒疫苗中的 2 型血清成分被撤回。采取这一措施是为了防止减毒活疫苗突变引起的疫苗相关疾病暴发。目前，世界各地的儿童对 2 血清型脊髓灰质炎病毒的免疫力很差，因为灭活疫苗的效果要差得多，而且新的口服疫苗尚未准备就绪。 Macklin 等人使用统计模型。发现目前在亚洲和撒哈拉以南非洲的几个国家爆发的大多数脊髓灰质炎疫情可能与 2 型血清疫苗株有关（参见 Donlan 和 Petri 的观点）。为了在脊髓灰质炎病毒爆发时阻止传播，需要部署盒子里唯一的工具：现有的减毒血清 2 型口服活疫苗，这会增加疫苗衍生疾病的风险。科学，本期第 14 页。 401;另见 p. 362 2 型血清疫苗衍生的脊髓灰质炎病毒的爆发可以追溯到疫情应对活动中口服脊髓灰质炎病毒疫苗的使用。尽管 20 多年来没有出现 2 型野生脊髓灰质炎病毒病例，但 2 血清型疫苗衍生脊髓灰质炎病毒 (VDPV2) 和相关麻痹病例在几大洲的传播对根除构成了威胁。 2016 年 4 月，撤销了口服脊髓灰质炎病毒疫苗 (OPV2) 2 血清型成分，以阻止 VDPV2 的出现并确保根除所有 2 血清型脊髓灰质炎病毒。在全球范围内，该日期之后出生的儿童预防传播的免疫力有限。使用统计模型，我们估计了 2016 年 5 月至 2019 年 11 月期间检测到的 VDPV2 的出现日期和来源。 使用单价 OPV2 进行疫情应对活动是诱导免疫力以防止传播的唯一可用方法。然而我们的分析表明，使用单价 OPV2 会导致更多麻痹性 VDPV2 爆发，并有可能形成地方性传播。迫切需要一种新型 OPV2（目前有两种候选疫苗正在进行临床试验），以及如果这种疫苗没有实现或未按预期发挥作用的应急策略。