University of Liberia-Pacific Institute for Research & Evaluation (UL-PIRE) Africa Center, University of Liberia, Monrovia, Liberia; West African Consortium for Clinical Research on Epidemic Pathogens (WAC-CREP), Monrovia, Liberia.
Polio Eradication, World Health Organization, Geneva, Switzerland.
Lancet Glob Health. 2023 Jun;11(6):e917-e923. doi: 10.1016/S2214-109X(23)00116-X.
Novel oral poliovirus vaccine type 2 (nOPV2) was administered in Liberia in response to an outbreak of circulating vaccine-derived poliovirus type 2 (cVDPV2) in 2021. We conducted a serological survey of polio antibodies after two national campaigns with nOPV2.
This clustered, cross-sectional, population-based seroprevalence survey was conducted in children aged 0-59 months, more than 4 weeks after the second nOPV2 vaccination round. We used a clustered sampling method in four geographical regions of Liberia, followed by a simple random sampling of households. One eligible child was randomly selected per household. Dried blood spot specimens were taken and vaccination history was recorded. The antibody titres against all three poliovirus serotypes were assessed using standard microneutralisation assays done at the US Centers for Disease Control and Prevention in Atlanta, GA, USA.
Analysable data were obtained from 436 (87%) of 500 enrolled participants. Of these, 371 (85%) children were reported via parental recall to have received two nOPV2 doses, 43 (10%) received one dose, and 22 (5%) received no doses. The seroprevalence against type 2 poliovirus was 38·3% (95% CI 33·7-43·0; 167 of 436 participants). No significant difference was observed between type 2 seroprevalence in children aged 6 months or older who were reported to have received two doses of nOPV2 (42·1%, 95% CI 36·8-47·5; 144 of 342), one dose (28·0%, 12·1-49·4; seven of 25), or no doses (37·5%, 8·5-75·5; three of eight; p=0·39). The seroprevalence against type 1 was 59·6% (54·9-64·3; 260 of 436), and the seroprevalence against type 3 was 53·0% (48·2-57·7; 231 of 436).
Unexpectedly, the data showed low type 2 seroprevalence after two reported doses of nOPV2. This finding is probably affected by the lower oral poliovirus vaccine immunogenicity previously demonstrated in resource-limited settings, with high prevalence of chronic intestinal infections in children and other factors discussed herein. Our results provide the first assessment of nOPV2 performance in outbreak response in the African region.
WHO and Rotary International.
2021 年，利比里亚出现循环疫苗衍生脊髓灰质炎病毒 2 型（cVDPV2）疫情，该国使用新型口服脊髓灰质炎病毒 2 型（nOPV2）开展了两次全国疫苗接种运动。我们在两轮 nOPV2 接种后开展了一项脊髓灰质炎抗体血清学调查。
这项聚类、横断面、基于人群的血清流行率调查在年龄在 0-59 个月的儿童中开展，于两轮 nOPV2 接种后超过 4 周进行。我们在利比里亚的四个地区采用聚类抽样方法，然后对家庭进行简单随机抽样。每个家庭随机抽取一名符合条件的儿童。采集干血斑标本并记录疫苗接种史。使用美国亚特兰大疾病控制与预防中心（CDC）的标准微量中和测定法评估所有三种脊髓灰质炎病毒血清型的抗体滴度。
在 500 名入组的参与者中，有 436 名（87%）提供了可分析数据。其中，371 名（85%）儿童经家长回忆报告称已接受两轮 nOPV2 接种，43 名（10%）接受一轮接种，22 名（5%）未接种。2 型脊髓灰质炎病毒血清流行率为 38.3%（95%CI33.7-43.0；436 名参与者中有 167 名）。报告接受两轮 nOPV2 接种（42.1%，95%CI36.8-47.5；342 名儿童中有 144 名）、一轮接种（28.0%，12.1-49.4；25 名儿童中有 7 名）或未接种（37.5%，8.5-75.5；8 名儿童中有 3 名）的儿童中，2 型血清流行率无显著差异（p=0.39）。1 型血清流行率为 59.6%（54.9-64.3；436 名儿童中有 260 名），3 型血清流行率为 53.0%（48.2-57.7；436 名儿童中有 231 名）。
两轮 nOPV2 报告接种后，数据显示 2 型血清流行率出乎意料地较低。这一发现可能受到先前在资源有限环境中口服脊髓灰质炎疫苗免疫原性较低的影响，也可能受到儿童中慢性肠道感染高发和本文讨论的其他因素的影响。本研究结果提供了首次对非洲区域 nOPV2 在疫情应对中的表现进行的评估。
世界卫生组织和 Rotary国际。
