The Impact of Rotavirus Vaccines on Genotype Diversity: A Comprehensive Analysis of 2 Decades of Australian Surveillance Data

Background. Introduction of rotavirus vaccines into national immunization programs (NIPs) could result in strain selection due to vaccine-induced selective pressure. This study describes the distribution and diversity of rotavirus genotypes before and after rotavirus vaccine introduction into the Australian NIP. State-based vaccine selection facilitated a unique comparison of diversity in RotaTeq and Rotarix vaccine states. Methods. From 1995 to 2015, the Australian Rotavirus Surveillance Program conducted genotypic analysis on 13 051 rotavirus-positive samples from children <5 years of age, hospitalized with acute gastroenteritis. Rotavirus G and P genotypes were determined using serological and heminested multiplex reverse-transcription polymerase chain reaction assays. Results. G1P[8] was the dominant genotype nationally in the prevaccine era (1995-2006). Following vaccine introduction (2007-2015), greater genotype diversity was observed with fluctuating genotype dominance. Genotype distribution varied based on the vaccine implemented, with G12P[8] dominant in states using RotaTeq, and equine-like G3P[8] and G2P[4] dominant in states and territories using Rotarix. Conclusions. The increased diversity and differences in genotype dominance observed in states using RotaTeq (G12P[8]), and in states and territories using Rotarix (equine-like G3P[8] and G2P[4]), suggest that these vaccines exert different immunological pressures that influence the diversity of rotavirus strains circulating in Australia.