Dynamics of G2P[4] strain evolution and rotavirus vaccination: A review of evidence for Rotarix.

Rotavirus (RV) gastroenteritis is a vaccine-preventable disease that creates high medical and economic burden in both developed and developing countries. Worldwide, more than 100 countries have introduced RV vaccines in their national immunization programs, and the remarkable impact of reducing the burden of severe childhood gastroenteritis has been unequivocally demonstrated. Currently, 2 oral vaccines (Rotarix, GSK and RotaTeq, Merck) are widely utilized. Recent temporary increases in the relative prevalence of G2P[4] RV strains have been observed in countries implementing RV vaccination. This comprehensive literature review aims to provide an insight on RV genotype evolution in the context of mass vaccination with Rotarix, particularly in the case of G2P[4]. In the post-vaccine era, strain surveillance data indicated temporal and spatial changes in countries both with and without RV vaccination programs. Annual fluctuations in G2P[4] prevalence seem to occur naturally, with no substantial differences between countries using Rotarix, RotaTeq or mixed vaccination programs. Moreover, Rotarix has been shown to be efficacious and effective against gastroenteritis caused by non-vaccine strains, including G2P[4]. These data indicate that shifts in RV genotype distribution are likely to constitute an inherent process of virus evolution to infect the human gut. Following RV vaccine introduction, incidences of RV gastroenteritis declined dramatically and mass vaccination will likely maintain this status, despite possible fluctuations in the relative distribution of genotypes. There is no conclusive evidence of unusual burst of new or vaccine-escape strains since global RV vaccines use. The emergence of strains with a potential to increase the current burden of RV disease should be continuously monitored and can only be established by exhaustive characterization of strains, including whole genomic sequencing. Given the natural fluctuations in RV strains over time, caution is advised when interpreting temporal changes in RV strain dynamics, as they could mistakenly be attributed to vaccination.