Utilization of Hospital-Based Sentinel Surveillance for Gastroenteritis to Evaluate the Long-Term Impact of Rotavirus Vaccine After Vaccine Introduction into the Togolese Immunization Schedule

Introduction: Rotavirus remains the leading cause of severe gastroenteritis in young children worldwide despite widespread evidence of the positive impact of rotavirus vaccine. We evaluated the long-term impact of rotavirus vaccine introduction on rotavirus diarrhea hospitalizations in Togo. Method: We implemented active surveillance for all cause gastroenteritis in Togolese children < 5 years of age hospitalized at Sylvanus Olympio Teaching Hospital in Lome. Rotavirus testing with ELISA was performed at the sentinel site laboratory and genotyping performed at regional laboratories on stool samples collected from these children. To assess long term impact of rotavirus vaccine, we compared findings pre vaccine (2010-2014) and post vaccine (2015-2024) introduction. Results: Overall, 1,507 children hospitalized with all cause gastroenteritis were enrolled in the surveillance study, and 1,444 (95.8%) had rotavirus ELISA result, including 65.6% before rotavirus vaccine introduction. Of these 1,444 cases, annual median number of 189 (range=153-260) all-cause gastroenteritis hospitalizations before vaccine declined to 40 (range=27–71) after vaccine introduction, a 78.8% annual median reduction. Rotavirus-associated annual median prevalence decreased from 54.0% to 16.9% (range=5.3-41.3%) after vaccine introduction, and proportion rotavirus positive in < 1 year old infants decreased from 64.0% to 34.5%. The number of non-rotavirus gastroenteritis cases before and after vaccine introduction remained stable, while rotavirus cases became too small to allow appreciation of its seasonality after vaccine introduction. We observed a predominance of G1P[8] in 47.5% of cases, followed by G2P[4] in 10.2% of cases after vaccine introduction. Conclusions: We observed evidence of sustained impact of rotavirus vaccine, with a substantial decline in rotavirus gastroenteritis cases in Togo. Continuing surveillance will remain important to better monitor additional changes in rotavirus disease in Togo.