Higher proportion of G2P[4] rotaviruses in vaccinated hospitalised cases compared to unvaccinated hospitalised cases, despite high vaccine effectiveness against heterotypic G2P[4] rotaviruses

The overall vaccine effectiveness of the monovalent rotavirus vaccine in an observational, prospective, multicentre, hospital-based case-control study in Belgium (RotaBel) was 90%. However, rotavirus genotype and co-infecting pathogens are important parameters to take into account when assessing vaccine effectiveness. In this study we specifically investigated the effect of rotavirus genotypes and co-infecting pathogens on vaccine effectiveness for the monovalent vaccine. In addition, we also investigated the effect of co-infecting pathogens on disease severity. From February 2008 to June 2010 stool samples of rotavirus gastroenteritis cases of a random sample of 39 Belgian hospitals were collected and subsequently genotyped. Fisher's exact tests were performed to investigate the relationships between rotavirus genotype, co-infecting pathogens and disease severity. The vaccine effectiveness of a full series of the monovalent rotavirus vaccine against hospitalised rotavirus gastroenteritis caused by G1P[8] rotavirus strains was 95%[95% CI:77.5-98.7]. Against G2P[4], the vaccine effectiveness was 85%[CI:63.7-93.8]. G4P[8]- and G3P[8]-specific vaccine effectiveness was 90%[CI:19.2-98.7] and 87%[CI:-5.2-98.4], respectively. A post-hoc analysis showed that the genotype distribution was significantly related to the vaccination status (P