Comprehensive reviews of pre licensure rotavirus strain prevalence data indicated the global importance of six rotavirus genotypes, G1P[8], G2P[4], G3P[8], G4P[8], G9P[8] and G12P[8]. Since 2006, two vaccines, the monovalent Rotarix (RV1) and the pentavalent RotaTeq (RV5) have been available in over 100 countries worldwide. Of these, 60 countries have already introduced either RV1 or RV5 in their national immunization programs. Post licensure vaccine effectiveness is closely monitored worldwide. This review aimed at describing the global changes in rotavirus strain prevalence over time. The genotype distribution of the nearly 47,000 strains that were characterized during 2007-2012 showed similar picture to that seen in the preceding period. An intriguing finding was the transient predominance of heterotypic strains, mainly in countries using RV1. Unusual and novel antigen combinations continue to emerge, including some causing local outbreaks, even in vaccinated populations. In addition, vaccine strains have been found in both vaccinated infants and their contacts and there is evidence for genetic interaction between vaccine and wild-type strains. In conclusion, the post-vaccine introduction strain prevalence data do not show any consistent pattern indicative of selection pressure resulting from vaccine use, although the increased detection rate of heterotypic G2P[4] strains in some countries following RV1 vaccination is unusual and this issue requires further monitoring.

Group A rotavirus (Rotavirus A, RVA) is the main cause of acute dehydrating diarrhea in humans and numerous animal species. RVA shows vast diversity and a variety of human strains share genetic and antigenic features with animal origin RVA strains. This finding suggests that interspecies transmission is an important mechanism of rotavirus evolution and contributes to the diversity of human RVA strains. RVA is responsible for half a million deaths and several million hospitalizations worldwide. Globally, two rotavirus vaccines are available for routine use in infants. These vaccines show a great efficacy profile and induce protective immunity against various rotavirus strains. However, little is known about the long-term evolution and epidemiology of RVA strains under selective pressure related to vaccine use. Continuous strain surveillance in the post-vaccine licensure era is needed to help better understand mechanisms that may affect vaccine effectiveness.