Review of global rotavirus strain prevalence data from six years post vaccine licensure surveillance: is there evidence of strain selection from vaccine pressure?

Abstract

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.

Keywords: Genotype; RotaTeq; Rotarix; Rotavirus; Surveillance.

Fig. 1.

Geographical distribution of medically important RVA strains between 2007 and 2012. WHO regions are highlighted by various colors; dark shade shows countries providing data from any given region. In addition to the six globally common G–P combinations, regionally common, unusual and rare strains are also shown and referred to as ‘Other’. Mixed infection with multiple G and/or P types and non-typeable strains were not included in the calculations.

Fig. 2.

Spatiotemoral shift in predominance of the globally common six G–P combinations and some others. Data were broken down by study year whenever possible. Color codes refer to a particular G–P combination. Diagonal color patterns indicate two different G–P combinations circulated at similar great prevalence. The dates when universal RVA vaccination was implemented in a given country and the prefererred RVA vaccine are indicated where relevant.

Fig. 3.

Evolution of RV vaccines. The virions and the parental genomic constellations of RV1 and RV5 are shown in orange and green, respectively. Wild type strains are represented by blue color. Missing sequence information is shown as empty bars.