Backgrounds:

We aim to assess whether a switch to non-G1P[8] strains and greater strain diversity post-rotavirus vaccine introduction is associated with vaccination or due to natural fluctuations in strain types across Europe.

Methods

The study area includes 23 countries submitting data to either EuroRotaNet or the WHO EURO Sentinel Surveillance Network for Rotavirus. Epidemiological and microbiological data was collected on genotyped rotavirus-positive samples between 2006 and 2018.

To investigate the effect of vaccination on strain types we will fit Bayesian multinomial logistic regression models, with genotype as the outcome. Generalized linear mixed-effect models will be used to analyse the effect of vaccination on strain diversity and richness.

Results:

Descriptive analysis of EuroRotaNet countries

In the twelve countries contributing to EuroRotaNet, 62,773 samples were characterised during the study period. Seven genotypes contributed 97% of single rotavirus strain typed specimens: G1P[8]; G4P[8]; G2P[4]; G9P[8]; G3P[8]; G12P[8]; and G9P[4]. Since the introduction of routine vaccination in the UK and Germany in 2013 the prevalence of G1P[8] has fallen (Figure 1). In the UK the prevalence of G2P[4] has increased since vaccine introduction, peaking at 79% in 2016/17. However, in 2017/18 in the UK the strain distribution was more diverse, and G3P[8] accounted for 24% of single typed strains. In countries without widespread rotavirus vaccination, there has been a shift since 2015/16 to non-G1P[8] genotypes.

Conclusions/Learning Points:

The consistent decline in G1P[8] strains across both countries with and without infant rotavirus immunization schedules may suggest either that the increase in vaccinated cohorts across Europe is having an impact across borders or that natural fluctuations in strain distributions have coincided with increased rotavirus vaccination across Europe. The statistical analyses are in progress and will allow us to elucidate firmer conclusions.