Sustained reduction in rotavirus-coded hospitalizations in children aged <5 years after introduction of self-financed rotavirus vaccines in Japan

A Multi-Pathogen Retrospective Study in Patients Hospitalized for Acute Gastroenteritis

Acute gastroenteritis (AGE) is a gastrointestinal tract disease often caused by consuming food or water contaminated by bacteria, viruses, or parasites, that can lead to severe symptoms requiring hospitalization. A retrospective study on patients admitted for AGE between 2021 and 2023 at the Pediatrics and Infectious Diseases Departments of Lecce Hospital was conducted. Demographic characteristics, year and month of admission, length of hospital stay, etiological agents, co-infections, and blood chemistry data of patients were collected. The study included 103 patients ranging in age from 0 to 15 years, with 58.25% being male. A total of 78 bacterial, 35 viral, and 7 parasitic infections were identified. The most commonly detected pathogens were Escherichia coli (38.83%), Norovirus (28.16%), Campylobacter jejuni (22.33%), and Salmonella typhi/paratyphi (10.68%). Only a few cases of Cryptosporidium (5.83%) were identified. Additionally, 17 co-infections (16.50%) were detected. Viral infections are the primary cause of hospitalization for AGE in children <5 years, while bacterial infections are more common among older patients. The significantly higher number of children <5 years old with elevated creatinine compared to children ≥5 years suggested that young children are more susceptible to dehydration than older children. Few cases of AGE were attributed to pathogens for which a vaccine has already been licensed. AGE is a serious health concern that could be effectively prevented by implementing food-based and community-level sanitation systems, as well as by increasing vaccination coverage of available vaccines and developing new effective and safe vaccines.

Rotavirus genotypes and clinical outcome of natural infection based on vaccination status in the post-vaccine era

Rotavirus (RV) is a leading cause of gastroenteritis in children. In Japan, Rotarix (RV1; GlaxoSmithKline), which is a monovalent vaccine derived from human RV (G1P[8]), has been introduced since November 2011, and RotaTeq (RV5; MSD) which is an pentavalent, human-bovine mono-reassortant vaccine (G1, G2, G3, G4, and P1A[8]), has been introduced since July 2012. Long-term follow-up on vaccine efficacy and RV genotypical change should be carried out in order to control RV infection. The RV gastroenteritis (RVGE) outbreak occurred during the 2018/2019 season in Aichi prefecture, Japan. Therefore, the molecular epidemiology of RV among three different groups of RVGE, which were outpatients who received RV1, those who received RV5, and those without vaccination, was explored. Clinical features of RVGE patients were compared among the three patient groups. Children less than 15 years of age with gastroenteritis who visited any of seven pediatric practices between January and June 2019 were enrolled in the study. G, P, and E genotypes were determined by direct sequencing of reverse transcription-polymerase chain reaction products amplified from stool samples. Among 110 patients, there were 27, 28, and 55 in the RV1-vaccinated, RV5-vaccinated, and unvaccinated groups, respectively. The most frequent genotype was G8P[8] (92/110 patients, 83.6%). Genotype distributions did not significantly differ among the three patient groups (P = .125). Mean Vesikari score was significantly lower among RV1-vaccinated (7.1) and RV5-vaccinated patients (6.4) than among unvaccinated patients (10.2) (P < .001). Even in RVGE patients treated in an outpatient clinic, RV vaccine reduced the severity of the disease in this cohort.

Clinical and Epidemiologic Features of Viral Gastroenteritis in Hospitalized Children: An 11-Year Surveillance in Palermo (Sicily)

In order to acquire information regarding viral agents and epidemiologic features of severe paediatric Viral Acute Gastroenteritis (VAGE) across multiple seasons in the pre-rotavirus-vaccine era, the epidemiologic characteristics of VAGE were investigated among paediatric patients hospitalized in a major Sicilian paediatric hospital from 2003 to 2013. Overall, 4725 children were observed and 2355 (49.8%) were diagnosed with a viral infection: 1448 (30.6%) were found positive to rotavirus, 645 (13.7%) to norovirus, 216 (4.6%) to adenovirus, and 46 (0.97%) to astrovirus. Viral infections showed different patterns of hospitalization in terms of age at risk (younger for rotavirus and adenovirus infections), seasonality (increased risk in winter for rotavirus and norovirus), trend over time (reduced risk in 2011-2013 for norovirus and rotavirus) and major diagnostic categories (digestive diseases more frequent in adenovirus and astrovirus but not in norovirus). This study increases general knowledge of VAGE epidemiology and contributes to suggest some a priori diagnostic criteria that could help clinicians to identify and treat viral agents responsible for gastroenteritis in hospital settings.

Effectiveness of self-financed rotavirus vaccination in Ise City, Japan

In Japan, the herd immunity effect of rotavirus vaccine has not yet been proven. Here, we conducted active surveillance for hospitalization due to rotavirus acute gastroenteritis (AGE) among children under 5 years of age in pre-rotavirus vaccination years and self-financed rotavirus vaccination years to clarify the rotavirus vaccine effectiveness (VE) in reducing hospitalization rates. A time-series analysis showed that the monthly hospitalization rates observed after vaccine introduction were significantly lower than the forecasted hospitalization rates (p < .001, Mann-Whitney U test). In the third year after vaccine introduction, the hospitalization rate declined despite the low vaccination rate of 27-50% for the two preceding years. We estimated four types of VE, namely direct, indirect, total, and overall. The direct VE was calculated from the relative risk ratio of hospitalizations between vaccinated and unvaccinated children. The indirect VE was defined as the population-level effects of vaccination on children not receiving the vaccine. The total VE was defined as the combination of the direct and indirect VE on children receiving the vaccine. The overall VE was determined by the weighted average of indirect VE on the children not receiving the vaccine and the total VE on the children receiving the vaccine. The direct, indirect, total, and overall VE values were calculated as 82% (95% confidence interval, 52-93), 70% (51-82), 95% (87-98), and 86% (77-91), respectively. The high values of indirect, total, and overall VE indicate that the rotavirus vaccine produces a herd immunity effect.