The Emergence and Predominance of the G3 Genotype after Rotarix Introduction in Senegal

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Background: After national introduction of the monovalent Rotavirus vaccine (Rotarix®, G1P[8]) in Senegal in November 2014, sentinel surveillance at Albert Royer National Children’s Hospital Center recorded shifts in circulating Rotavirus genotypes. We report molecular surveillance data collected from 2015-2020 and compare pre- and post-vaccine genotype distributions to document the emergence of G3 and its VP7/VP4 combinations. Methods: Stool specimens were collected from children under 5 years of age who were hospitalized or under observation at the Albert Royer National Children’s Hospital in Dakar from January 1st 2015 to December 31, 2020. Rotavirus antigen detection was performed using an enzyme-linked immunosorbent assay (ELISA), and molecular characterization of ELISA-positive samples was conducted at the West African Regional Rotavirus Reference Laboratory in Accra, Ghana. Results: During the pre-vaccine period (2010-2014), a total of 683 stool specimens were collected, of which 333 tested positive for Rotavirus, corresponding to a positivity rate of 48.76 %. This rate declined to 15.29 % in the post-vaccine period (2015-2020), when 89 of 582 samples were positive. The p value indicates a statistically significant difference (p<0.05). In the pre-vaccine period, VP7 genotyping (n=177) identified G1 and G12 as predominant; VP4 was dominated by P[8] (57.90 %), and the most frequent combination was G12P[8] (28.80 %). In the post-vaccine period (2015-2020), G3 emerged as the predominant VP7 genotype from 2018 onward. Among post-vaccine genotyped strains (n=78), G3 accounted for the majority with main combinations of G3P[8] (18.20 %) and G3P[6] (9.90 %); mixed VP4 profiles (P[8]P[6], P[4]P[6]) were also detected. The post-vaccine emergence of rotavirus genotype G3, replacing previously dominant G1 and G12 strains, indicates a shift in viral ecology under vaccine-induced immune pressure. Conclusions: Sentinel surveillance at Albert Royer Hospital documents a genotype shift from G1P[8]/G12P[8] pre-vaccine to predominance of G3 and G3P[8]/G3P[6] combinations in the post-vaccine era. The emergence of G3 strains after Rotarix introduction raises concerns about possible antigenic mismatch and the need to monitor vaccine effectiveness over time. These findings underline the need for continued molecular surveillance and whole-genome characterization to monitor vaccine impact and viral evolution in West Africa.

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