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.