Rotavirus (RV) in Japan vaccines have been introduced but have not been used since 2018 for universal vaccination. Therefore, in children less than three years of age the study identified instances of severely rotavirus gastroenteritis (RVGE) and we examined the onset of infections before and after the introduction of RV vaccinations. In 4 paediatric clinics in Shibata City, Niigata Prefecture, Japan a prospective ecological monitoring study was done in the RGGE epidemic seasons from 2011 to 2018. The study period was separated into three periods: Pre-vaccine initiation (2011), low-mediate transitional coverage and high level of coverage (67.7– 81.7 percent from 2015 to 2018).

The incidence of severe RVGE in this study at the plateau age was much lower than in Pre-Vaccine and Transitional Ages. Moreover, in the plateau period, hospitalisation rates because of RVGE were lower than in pre-vaccination and transitional times in Shibata City. With the growth in the levels of vaccine coverage by more than 70 per cent over the plateau era, the number of RVGE hospitalizations in people who required or did not require intravenous rehydration at paediatric clinics dropped considerably.