Y. I. Kyrlan

In Russia, viral agents dominate the etiological structure of аcute intestinal infections (AII), with rotavirus and norovirus playing the major role. Vaccination against rotavirus infection (RVI) demonstrates high efficacy (78—94%) in preventing severe forms requiring hospitalization. The introduction of rotavirus vaccination has altered the etiological landscape; however, the clinical features of AII in vaccinated children, including breakthrough infections and coinfections, remain insufficiently studied. Objective : to analyze the course of acute intestinal infections (AII) in unvaccinated and rotavirus-vaccinated children aged 8 months to 3 years. Materials and methods . A prospective observational cohort study was conducted at the G.N. Speransky Children's City Clinical Hospital (Moscow) in 2023—2024. The study included 205 patients hospitalized with AII within the first three days of symptom onset. Two groups were formed: children vaccinated against RVI (n = 93) and unvaccinated children (n = 112). Etiological diagnosis was performed by PCR; rotavirus genotyping was carried out (Sanger sequencing). Statistical analysis included the Mann—Whitney U test, Pearson's chi-squared test, calculation of odds ratios (OR) and 95% confidence intervals (CI). Results. The groups were comparable in sex, age, and time of hospitalization (median — second day of illness). Vaccinated patients had a significantly shorter duration of illness: median 5 days [4;5] versus a longer course in the unvaccinated group (p = 0.033). The frequency of gastroenteritis in the vaccinated group was almost twofold lower — 29.0% (95% CI: 20.4—38.6%) compared to 56.6% (95% CI: 46.7—65.3%) in the comparison group (p = 0.001). Rotavirus was detected significantly less often in vaccinated children: 10/93 (10.8%) versus 41/109 (37.6%) in unvaccinated children (χ² = 17.79; p < 0.0001; OR = 0.200; 95% CI: 0.093—0.428). The detection rate of norovirus did not differ between the groups (30.1% vs 20.2%; p = 0.143). Campylobacter was detected more frequently in vaccinated children: 12/93 (12.9%) versus 4/109 (3.7%) (p = 0.031; OR = 3.89; 95% CI: 1.21—12.51); however, the authors note the possibility of Berkson's bias due to the small number of cases. Among vaccinated children with confirmed rotavirus infection (n = 10), hyperthermia above 39°C was not recorded (0%), whereas in the unvaccinated group (n = 42) this symptom was observed in 31% (95% CI: 16.7—45.0%). The predominant rotavirus genotype in both groups was G3[P8].