Genotype Diversity of Rotavirus in Odisha, India: Postvaccine Changes

The inclusion of the ROTAVAC^® and ROTASIIL^® vaccines into India's Universal Immunization Program in 2016 and 2018, respectively, aimed to reduce the burden of acute gastroenteritis (AGE) due to rotavirus among children aged < 5 y. This study evaluated the impact of the vaccines on rotavirus genotype distribution and prevalence between 2014 and 2023 in Odisha.

Clinical data and vaccination records of children aged < 5 y with AGE enrolled across multiple tertiary centers in Odisha were collected through hospital-based surveillance. Stool samples were collected and tested for rotavirus antigen using enzyme immunoassay. Positive samples were genotyped using reverse transcription-polymerase chain reaction.

Of the 6,233 stool samples tested, 37.1% were positive for rotavirus. Positivity declined from 60.2% in 2014 to 23.3% in 2023, representing a 61.3% relative reduction. A significant shift in genotype prevalence was observed after vaccine introduction. G1P[8], the predominant strain in the prevaccine era (45.6%), decreased in prevalence and disappeared after 2018. G3P[8] emerged as a predominant strain during the postvaccination period, and G2P[4] resurged, representing 40.9% of cases in 2023. Mixed infections constituted 14.8% of samples, highlighting ongoing genetic diversity.

The introduction of rotavirus vaccines has reduced the prevalence of rotavirus infections and altered the rotavirus genotype distribution in Odisha. The predominance of G3P[8] and resurgence of G2P[4] indicate evolving strain dynamics after vaccine introduction. This study, thus, highlights the importance of vaccination programs in mitigating rotavirus-associated morbidity, emphasizing the need for sustained monitoring to guide future vaccine strategies.