The prevalence of rotavirus infection among Congolese children younger than 5 years hospitalized for gastroenteritis 10 years after introduction of rotavirus vaccination

Objectives: Rotavirus A (RVA) remains the primary cause of acute severe gastroenteritis associated with high rates of childhood hospitalization and mortality worldwide. The prevalence of RVA infection varies within low-income countries. In addition, its genetic diversity may vary among regions and may affect its prevalence. To control the emergence of new strains of RVA circulating in the Republic of Congo, it is essential to know the diversity of both G and P genotypes, which could render the vaccine less effective. Therefore, this study aimed to determine the prevalence and genotype diversity of RVA strains in children who were hospitalized, whether vaccinated or not. Moreover, the potential risk factors of disease severity are identified. Methods: The study was conducted from April 2022 to March 2023. Stool samples were collected from children younger than 5 years, hospitalized in a pediatric ward for acute gastroenteritis, and a commercial enzymelinked immunosorbent assay (ELISA) was used to detect RVA cases. In parallel, a multiplex reverse transcriptionpolymerization chain reaction (RT-PCR) was performed for RVA detection and genotyping. All samples with ambiguous multiplex RT-PCR results were subjected to sequencing. Results: A total of 227 children hospitalized were enrolled and tested for RVA infection. Using ELISA and PCR, 59 (26%) and 131 (57.7%) individuals were found to be infected with RVA, respectively. All individuals with a positive ELISA test result were confirmed as RVA-positive by PCR. Of the 98 children with documented histories of RVA vaccination, 60% presented with RVA infection. The occurrence of vomiting on more than three occasions within a 24-hour period and the time between vaccination and sample collection were found to be associated with RVA infection. RVA genotyping revealed six P types (P[4]; P[6]; P[8]; P[9]; P[10]; and P[11]). The predominant genotypes were (P[4] 15.3%; P[6] 13.7%; P[8] 22.1%; P[9] 14.5%). Among the eight G types, the most prevalent were G3 (13.7%), G4 (12.2%), and G1 (6.9%). No specific genotype distribution was discernible as a function of vaccination history. Conclusions: Compared with the findings of our study before the implementation of rotavirus vaccination, in this report, we observed a roughly 20% decreased prevalence of RVA infection in children hospitalized. The results suggest that in Brazzaville at least, 10 years of rotavirus vaccination in the Republic of Congo have had a substantial effect, despite the reported reduced efficacy of the vaccines in low- and middle-income countries. The findings thus support enhanced efforts to increase coverage through national vaccination programs.