Lessons from Recent Measles Post-Campaign Coverage Surveys Worldwide.

Background: Measles elimination strategies include supplementary immunization activities (SIAs) to rapidly fill immunity gaps. Post-campaign coverage surveys (PCCSs) are recommended to assess SIA coverage. We characterized selected PCCSs performed following recent SIAs, highlighting specific challenges and strengths, and provide recommendations for improvement.

Methods: We extracted national SIA data from the global measles/MR SIA database for the period of 2020-2023 and reviewed PCCS reports available at the World Health Organization headquarters. We extracted selected information on PCCS implementation, including information about the implementer, sampling, and main results.

Results: Only 15 of 66 countries (23%) with a national-level SIA performed since 2020 had a PCCS report available. We reviewed those reports, plus six more, following three 2019 SIAs with a delayed PCCS and two PCCSs following large subnational SIAs (Kenya 2021 and Yemen 2023). All 24 PCCS reports available were from Gavi-eligible countries, with 15 from South Saharan Africa (Cameroon, the Democratic Republic of the Congo, and Ethiopia had two PCCSs). Eleven (45.8%) PCCSs were conducted within three months of the end of the SIA. All included sampling information and most had percentage of participation. Description of the interviewers' profiles varied but was limited. PCCS coverage was lower than administrative data in all but two instances. All PCCSs collected data on previous measles vaccination status that would allow exploring indicators on the SIA reaching previously measles zero-dose children. Of the 12 PCCSs reporting coverage among previously measles zero-dose children, nine reported coverage among this group of more than 50% (range: 12% and 91.6%).

Conclusion: Even though a PCCS following an SIA is recommended and a requirement in Gavi-supported countries, most SIAs are not followed by a PCCS and, when performed, the timeliness of survey implementation needs improvement. Recent PCCSs were independently conducted and reports included basic survey information, but analysis and presentation of survey results vary particularly for measles zero-dose-related indicators. More guidance and technical support on how to implement PCCSs, including standardization of reports and more in-depth PCCS analyses, may help improve reporting and use of available PCCS data.