BACKGROUND: Sierra Leone launched its COVID-19 vaccination in March 2021 and achieved 73.2% full coverage among individuals aged 12 and older by December 2022. In October 2022, the country introduced the human papillomavirus (HPV) vaccine for 10-year-old girls, leveraging infrastructure and lessons from the COVID-19 vaccine deployment. We conducted a COVID-19 vaccine post-introduction evaluation (cPIE) to document best practices, assess impact on routine immunization, and identify key levers that supported HPV vaccine rollout, and recommendations for future pandemic preparedness. METHODS: We adapted the World Health Organization COVID-19 Post-Introduction Evaluation tool and conducted 84 structured interviews with national, district, and health facility staff in six districts, complemented by a desk review. Qualitative data were analysed thematically. RESULTS: By October 2023, COVID-19 full vaccination coverage was estimated at 86.7% among people aged ≥ 12 years, and first-dose coverage exceeded 100% based on programme denominators, likely reflecting uncertainty in population projections. Over 84% of doses were administered via surge campaigns and periodic intensification of routine immunization. Key lessons included: (1) delivering adult vaccination services closer to clients (e.g., schools, workplace, and homes); (2) re-tooling existing health infrastructure and systems; (3) engaging community leaders to build demand across the life-course; (4) strengthening electronic data systems for vaccination tracking; (5) integrating vaccines within one delivery platform; and (6) promoting operational innovations for rapid response. HPV vaccine uptake exceeded expectations, with 119% of the targeted girls vaccinated and 68% of doses administered in schools, supported by COVID-19 vaccination platforms, including cold chain, digital registries, and community mobilization networks. However, surge delivery approaches strained workforce capacity and were reported to disrupt routine immunization in some areas. CONCLUSION: Sierra Leone's experience highlights the feasibility of using emergency vaccination platforms to accelerate life-course vaccination and new vaccine introductions in low-resource settings. Sustained preparedness will require earlier integration guidance, strengthened coordination, financing, and improved data systems to support adult and adolescent immunization alongside routine services.
Kangbai et al. (2026) studied this question.