Circulating Vaccine‐Derived Poliovirus Type 2 (cVDPV2) Outbreak Response With Novel Oral Poliovirus Vaccine Type 2 (nOPV2), Sierra Leone's Experience

ABSTRACT Background In March 2024, a circulating vaccine‐derived poliovirus type 2 (cVDPV2) was isolated in environmental samples (ESs) collected at the Mabella Sawmill Bridge environmental surveillance (ES) site. The Ministry of Health and its partners responded to the outbreak by conducting a novel oral poliovirus vaccine type 2 (nOPV2) nationwide vaccination campaign among children aged 0–59 months. This study explores Sierra Leone's experience in terms of gaps identified, successes, and outcomes of the campaigns. Methods The study employed a descriptive secondary data analysis of the nOPV2 campaign, administrative, and lot quality assessment survey (LQAS). The LQAS is a cost‐effective survey methodology used to classify “lots” (districts) as having met or not met the predefined target threshold for the nOPV2 post‐vaccination campaign. Data were collected during the first round of the nOPV2 campaign in Sierra Leone in May 2024. Administrative data were extracted from the national nOPV2 campaign database, whereas the LQAS data were requested from the World Health Organization (WHO) server. Stata version 18 and Power BI were used to analyze the administrative and LQAS data. Results A total of 1,590,769 children aged 0–59 months were vaccinated against poliovirus in Sierra Leone. The supplementary immunization activity (SIA) coverage for the nOPV vaccination in Sierra Leone was 106% for the first round of the campaign. Moreover, of the 16 districts selected for the LQAS survey, 12 (75%) districts passed the study, and 4 (25%) districts failed the LQAS. Conclusion The first round of the nOPV2 vaccination campaign in Sierra Leone demonstrated significant success in reaching most of the target population, with robust preparatory and implementation strategies contributing to this achievement.