Effectiveness of Complete Rotavirus Vaccination Against Laboratory-Confirmed Rotavirus Gastroenteritis and Rotavirus-Associated Hospitalization in Children: An 11-Year Test-Negative Study

Background/Objectives: Rotavirus vaccination reduces severe childhood gastroenteritis, but real-world effectiveness may vary across settings and calendar periods. We estimated the effectiveness of documented complete rotavirus vaccination against laboratory-confirmed rotavirus gastroenteritis and rotavirus-associated hospitalization among children younger than 5 years in Türkiye. Methods: This retrospective test-negative study included children aged 0–59 months who underwent stool rotavirus testing for clinically evaluated acute gastroenteritis at a tertiary hospital between January 2015 and June 2026. Tests occurring within 14 days in the same child were combined into one episode. Cases were rotavirus-positive episodes and controls were rotavirus-negative episodes. Complete vaccination was defined by an institutional record showing completion of the full schedule before the index test. Cluster-robust logistic regression adjusted for age group, sex, treatment setting, calendar year, and test month. Vaccine effectiveness (VE) was calculated as (1−adjusted odds ratio)×100%. Results: The analysis included 2,788 episodes among 2,242 children: 534 rotavirus-positive cases and 2,254 test-negative controls. Complete vaccination was documented in 81 cases (15.2%) and 539 controls (23.9%). Crude VE was 43.1% (95% confidence interval [CI], 26.2%–56.1%). Adjusted VE against laboratory-confirmed rotavirus gastroenteritis was 52.8% (95% CI, 37.6%–64.3%; P<0.001). Among hospitalized episodes, adjusted VE was 57.8% (95% CI, 33.5%–73.2%; P<0.001). Estimates were stable when vaccination completion was required at least 14 days before testing, when only the first episode per child was retained, and with 7- or 30-day episode definitions. Effectiveness varied markedly by calendar period: 15.3% (95% CI, −28.7% to 44.3%) in 2015–2019 and 77.7% (95% CI, 62.3%–86.8%) in 2022–2026. Conclusions: Documented complete rotavirus vaccination was associated with substantially lower odds of laboratory-confirmed rotavirus gastroenteritis and rotavirus-associated hospitalization. The marked period-specific variation indicates that the pooled estimate should be interpreted with attention to changes in epidemiology, testing, healthcare utilization, and residual confounding across the COVID-19 era.