Effectiveness of self-financed rotavirus vaccines on acute gastroenteritis primary care episodes using real-world data in Spain: a propensity score–matched analysis of cohort study

The objective of this study was to estimate, by a novel spatiotemporal approach in an environment of non-funded rotavirus (RV) vaccines, the RV vaccine effectiveness (VE) to prevent acute gastroenteritis primary care (AGE-PC)–attended episodes, demonstrating how indirect protection leads to underestimation of direct VE under high vaccine coverage (VC). This population-based retrospective cohort study used electronic healthcare registries including all children 2 months–5 years old, born from 2009 to 2018 in the Valencia Region (Spain). Direct RV VE preventing AGE-PC episodes was estimated using propensity score matching and Poisson regressions stratified by VC, adjusted by age and calendar season. Indirect VE was estimated by Poisson regression comparing AGE-PC rates in unvaccinated children among the different VC levels. A total of 563,442 children were included for the RV VC estimation; of them, 360,576 were included in the birth-cohort for VE analysis. RV VC showed strong variability among districts and seasons, rising on average from 21