The (re-)emergence of these strains were accompanied by an unexpected global decline of G1 (mainly G1P) strains, a trend that was seen in at least 4 WHO regions over the last decade. Continued strain monitoring is required to see if such changes will continue and potentially accelerate in the post vaccine era, when most children will be immunized with vaccines containing antigens of the most common human strains resulting in possible immune selection pressure. Third, we documented
a remarkable diversity in circulating RV strains, with numerous newly reported G and P antigen combinations compared with 2 major review articles published only 5 years ago  and . This finding is likely related, in part, to improved genotyping methods and increased RV surveillance efforts preceding vaccine introduction. This great diversity of circulating RV strains could, in theory, prove challenging for vaccine development, this website but fortunately cross-protection
has been noted with both natural RV infection and with vaccine-induced immunity , , , ,  and . For example, in a recently completed efficacy trial in South Africa and Malawi, the monovalent G1P rotavirus vaccine appeared to provide comparable protection against the range of circulating rotavirus strains, including G8 strains that are somewhat unique to the African region, and to G2 and G12 strains which were totally heterologous to the vaccine . However, the role of homotypic and heterotypic immunity to rotavirus and the target antigens in heterotypic immunity continues to be debated, and, learn more as vaccines are introduced into routine immunization programs, opportunities to evaluate vaccine performance against partially or fully heterotypic strains should be pursued. Previous reviews have not accounted for variations in the availability of data from different settings, in particular the relative paucity of data from low income countries with the greatest RV mortality burden  and . Consequently, we were concerned that
an overall summary of strain data could distort the global picture of rotavirus strain prevalence, at least in terms of contributions to RV mortality. Given that available data do not indicate a consistent difference in virulence between various community acquired RV strains Rolziracetam , ,  and , we felt comfortable weighting our strain data based on mortality to ensure that the global and regional summaries appropriately give greater emphasis to strain data from countries with greatest contribution to rotavirus mortality. As expected, this adjustment increased the relative contribution of medically important strains in high mortality countries, compared with crude estimates. For example, whereas G8 strains that are prevalent in high RV mortality countries of Africa accounted for <1% of all strains during 2000–2003 (Fig.