Center of Excellence in Women and Child Health, The Aga Khan University, Karachi, Pakistan.
Department of Pediatrics and Child Health, The Aga Khan University, Karachi, Pakistan.
Front Public Health. 2024 Mar 27;12:1384410. doi: 10.3389/fpubh.2024.1384410. eCollection 2024.
After trivalent oral poliovirus vaccine (tOPV) cessation, Pakistan has maintained immunity to type 2 poliovirus by administering inactivated polio vaccine (IPV) in routine immunization, alongside monovalent OPV type 2 (mOPV2) and IPV in supplementary immunization activities (SIAs). This study assesses the change in poliovirus type 2 immunity after tOPV withdrawal and due to SIAs with mOPV2 and IPV among children aged 6-11 months.
Three cross-sectional sequential serological surveys were conducted in 12 polio high-risk areas of Pakistan. 25 clusters from each geographical stratum were selected utilizing probability proportional to size.
Seroprevalence of type 2 poliovirus was 49%, with significant variation observed among surveyed areas; <30% in Pishin, >80% in Killa Abdullah, Mardan & Swabi, and Rawalpindi. SIAs with IPV improved immunity from 38 to 57% in Karachi and 60 to 88% in Khyber. SIAs with IPV following mOPV2 improved immunity from 62 to 65% in Killa Abdullah, and combined mOPV2 and IPV SIAs in Pishin improved immunity from 28 to 89%. Results also reflected that immunity rates for serotypes 1 and 3 were consistently above 90% during all three phases and across all geographical areas.
The study findings highlight the importance of implementing effective vaccination strategies to prevent the re-emergence of poliovirus. Moreover, the results provide crucial information for policymakers working toward achieving global polio eradication.
三价口服脊髓灰质炎疫苗（tOPV）停用后，巴基斯坦通过在常规免疫中接种灭活脊髓灰质炎疫苗（IPV），以及在补充免疫活动（SIAs）中接种单价 OPV 型 2（mOPV2）和 IPV，维持了对 2 型脊髓灰质炎病毒的免疫力。本研究评估了 tOPV 停用后以及由于 mOPV2 和 IPV 的 SIAs 对 6-11 月龄儿童 2 型脊髓灰质炎病毒免疫力的变化。
在巴基斯坦 12 个脊髓灰质炎高风险地区进行了 3 次横断面序贯血清学调查。从每个地理区域利用大小比例概率选择了 25 个集群。
2 型脊髓灰质炎病毒的血清阳性率为 49%，在所调查的地区存在显著差异；皮辛地区<30%，基拉·阿卜杜拉、马尔丹和斯瓦比以及拉瓦尔品第地区>80%。在卡拉奇和开伯尔进行的 IPV 强化免疫将免疫力从 38%提高到 57%和 60%提高到 88%。在基拉·阿卜杜拉，继 mOPV2 之后进行的 IPV 强化免疫将免疫力从 62%提高到 65%，而在皮辛进行的 mOPV2 和 IPV 联合强化免疫将免疫力从 28%提高到 89%。结果还表明，在所有三个阶段和所有地理区域，1 型和 3 型的免疫率始终保持在 90%以上。
研究结果强调了实施有效疫苗接种策略以预防脊髓灰质炎病毒再次出现的重要性。此外，这些结果为致力于实现全球消灭脊灰的政策制定者提供了重要信息。
