Circulating Vaccine-Derived Poliovirus Type2 (cVDPV2) Outbreak Response with Novel Oral Poliovirus Vaccine type2 (nOPV2) May 2024, Sierra Leone’s Experience

Background: A circulating Vaccine-Derived Poliovirus Type 2 (cVDPV2) was isolated in environmental samples collected at the Mabella Sawmill Bridge environmental surveillance site in March 2024. 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) data collected during the first round of the nOPV2 campaign in Sierra Leone in May 2024. Administrative data was extracted from the national nOPV2 campaign database, while the LQAS data were requested from the WHO server. Stata version 18 and Power BI were used to analyse the administrative and LQAS data. Results: 1,590,769 children aged 0-59 months were vaccinated against the polio virus in Sierra Leone. The Supplementary Immunization Activity (SIA) coverage for the nOPV vaccination in Sierra Leone was 100% for the first round of the campaign. Also, of the sixteen districts selected for the LQAS survey, twelve districts 75% passed the survey, and four districts 25% failed the LQAS. Conclusion: The first round of the nOPV2 vaccination campaign in Sierra Leone demonstrated significant success in reaching the majority of the target population, with robust preparatory and implementation strategies contributing to this achievement.