Abstract
In Japan, monovalent and pentavalent rotavirus (RV) vaccines were approved in 2011 and 2012, respectively. To monitor the changes in the RV genotypes before and after vaccine introduction, we performed a prospective observational study among children (<5 years) with gastroenteritis who tested RV-positive on antigen rapid tests. Stool samples were collected from three different sites in Japan: Tsu City, Mie Prefecture; Kurashiki City, Okayama Prefecture; and Isumi City, Chiba Prefecture. RV genotypes were determined using reverse transcription-polymerase chain reaction. In Tsu City, G3P[8] was dominant (61.0–77.1%) before vaccine introduction, but decreased there. Meanwhile, in inverse proportion of the decrease in G3P[8], G1P[8] increased until the 2013/14 season, where a sudden dominance of G2P[4] (100%) occurred. A similar trend was observed in Kurashiki City in terms of the extent of the decrease in G3P[8] and the emergence of G2P[4]. In Isumi City, G1P[8] was dominant (70.3%) before vaccine introduction, whereas G9P[8] became dominant (83.3%) in the 2013/14 season. To determine whether the genotype changes are attributable to vaccines or natural epidemiological changes, ongoing continuous monitoring of the RV genotypes is required.
