Sailuenarm T.Phongsamart W.Bhunyakitikorn W.Doungngern P.Lapphra K.Wittawatmongkol O.Rungmaitree S.Lertamornkitti N.Vanprapar N.Maleesatharn A.Chokephaibulkit K.Mahidol University2026-06-092026-06-092026-07-01Lancet Regional Health Southeast Asia Vol.50 (2026)https://repository.li.mahidol.ac.th/handle/123456789/117201Background Rotavirus vaccination has reduced incidence of childhood diarrhoea, but evidence from low- and middle-income countries remains limited. We evaluated diarrhoea incidence and hospitalisation rates among children aged 0–59 months after introduction of rotavirus vaccination in Thailand’s national immunisation programme (February 2020–December 2024). Methods We analysed aggregated national surveillance data (ICD-10-TM: A00-A09, K56.1) from Thailand’s Health Data Centre (covering ≈90% of public health facilities), including inpatient, outpatient, and death records. Diarrhoea incidence and hospitalisation rates were assessed using Poisson regression to estimate incidence rate ratios (IRRs) among children 0-59 months of age with acute diarrhoea and among 0–11 months with intussusception. Vaccine impact was assessed by comparing pre-vaccination (2014–2019) and post-vaccination (2021–2024) periods, excluding the year 2020. Analyses were age-stratified as proxies for differential vaccine exposure across birth cohorts under the immunisation program. Findings Individual-level demographic characteristics were not available. All-cause and rotavirus-associated diarrhoea incidence declined by 50.0% (IRR 0.50; 95% CI 0.39–0.63) and 52.0% (IRR 0.48; 95%CI 0.39–0.59), respectively, following rotavirus vaccine introduction. Hospitalisation for all-cause and rotavirus-associated diarrhoea decreased by 58.2% (IRR 0.42; 95% CI 0.30–0.58) and 49.0% (IRR 0.51; 95%CI 0.30–0.88), respectively, at 1–4 years post-vaccination. All-cause acute diarrhoea mortality did not differ significantly during pre- and post-vaccination periods (IRR 0.94; 95% CI 0.50–1.77); rotavirus-specific mortalities were too few to analyse. Following vaccine introduction, seasonal peaks between December and February became less pronounced. Intussusception rates remained stable during the post-vaccination period (IRR 1.03; 95% CI 0.82–1.29). Interpretation This study demonstrated a significant decline in incidence and hospitalisation of all-cause and rotavirus-associated diarrhoea among children (0–59 months). Sustaining high coverage is essential to maximise public health benefits from vaccination. Funding None.MedicineArticleSCOPUS10.1016/j.lansea.2026.1007932-s2.0-10504067443027723682