Epidemiology and Clinical Impact of Pediatric Viral Gastroenteritis Before and After Rotavirus Vaccination in Sicily.

Acute gastroenteritis (AGE) remains a leading cause of pediatric mortality and morbidity, with rotavirus as the leading cause of severe disease. Post-vaccine surveillance is essential to monitor circulating pathogens and assess vaccination impact. Sicily was the first Italian region to implement universal rotavirus vaccination in 2012. We retrospectively studied 693 children hospitalized for suspected viral AGE at the Children's Hospital of Palermo (March 2017-February 2020), testing stool samples for viral and bacterial enteric pathogens. Rotavirus remained the most common agent (13.3%), followed by norovirus (12.1%), adenovirus (11.3%), Salmonella spp. (4.6%) and astrovirus (3.2%). The study population was categorized as rotavirus-associated AGE (RV-AGE) or other-cause AGE (O-AGE). Epidemiological, clinical and virological features were compared with the pre-vaccine period (2011-2012). At least one pathogen was detected in 47.5% of samples. RV-AGE cases were older than those with O-AGE (median 32.6 vs. 30.5 months; p < 0.01) and had greater clinical severity, with higher frequency of vomiting, fever and dehydration. Rotavirus infection was significantly associated with unvaccinated status. Compared with the pre-vaccine era, rotavirus prevalence declined (32.6% vs. 13.3%), seasonal patterns were attenuated and genotype distribution shifted toward G2P[4], G9P[8] and equine-like G3P[8] strains. Despite the decline in RV-AGE following vaccine introduction, rotavirus remains a relevant cause of pediatric AGE, underscoring the need for high vaccination coverage and continued surveillance.