Post-vaccine surveillance of Group A Rotavirus Strains circulating in the Littoral and South West Regions of Cameroon

Background: The effectiveness of Group A Rotavirus (RVA) vaccine in low-income countries has been limited, partly due to the circulation of strains not covered by existing vaccines. Despite the introduction of Rotarix (2014) in Cameroon, no nationwide studies have characterized circulating RVA strains. This study provides post-vaccination of RVA genotyping data from the Douala, Edea, Nkongsamba (Littoral) and Kumba (Southwest) regions of Cameroon. Methods: A cross-sectional study was carried out on 197 diarrheal samples and vaccination data collected from children under five from the Littoral region (n = 130; May 2015 - April 2016) and Kumba Southwest (n = 67; July 2017 - June 2018). RVA NSP3 gene was detected using qRT-PCR and the NSP3-positive samples underwent one-step multiplex RT-PCR for genotyping wild-type and vaccine strains, with VP4 and VP7 typing performed via nested PCR. Results: Of the 197 children, 63% were fully vaccinated with Rotarix, 22% were unvaccinated, and 15% had unknown status. A total of 87 samples were successfully genotyped (28 from Littoral, 59 from Kumba). Five VP7 (G) genotypes were identified: G1, G2, G3, G9, and G12. In Littoral, G2 (46.4%) and G3 (35.7%) predominated, while G1 (61%) and G12 (37.3%) were most common in Kumba. VP4 (P) genotypes included P[8], P[6], and P[4], with P[8] being most frequent in both regions. Mixed infections (3.6%) and non-typeable strains (7.1%) were also observed. Dominant G-P combinations included G3P[8] and G2P[4] in Littoral, and G1P[8] and G12P[6] in Kumba. Rare and partially typed strains were also detected. Conclusion: This study highlights the predominance of G1P [8] in vaccinated children and the emergence of non-vaccine-covered strains such as G2P [4], G3P [6], and G12P[6]. These findings underscore the need for ongoing surveillance and potential vaccine adjustments.