Severe rotavirus gastroenteritis in children older than 5 years after vaccine introduction

Introduction: Rotavirus (RV) is the major pathogen responsible for acute gastroenteritis in infants. Since RV vaccines were introduced, a substantial decline in the incidence of severe RV infection has been reported. However, some burden still exists, even in developed countries, including Japan. Methods: We retrospectively surveyed 380 patients hospitalized for acute gastroenteritis from 2015 to 2019. In 2019, additional detailed clinical information of 21 patients with RV gastroenteritis was obtained to evaluate the efficacy of the RV vaccine. Nine fecal samples from those patients were collected to detect the RV genotypes. Results: Our data showed an increasing trend in hospitalizations for severe RV gastroenteritis in children older than 5 years. According to the Vesikari clinical severity scores in the older group (≥5 years), the gastrointestinal symptoms in vaccinated patients were less severe than those in unvaccinated patients (p = 0.014). The genotype analysis revealed that G9P[8]I1 was the major genotype in the recruited patients in 2019. Conclusions: This report warns that children older than 5 years could be affected by severe RV infection and suggests prompt intervention for this age group, similar to that in infants. In the new period in which the RV vaccine is included in Japanese national immunization programs beginning October 2020, continuous monitoring of patient clinical characteristics and RV epidemiology is required to determine the role of vaccines.