Rotavirus epidemiology and genotype distribution in hospitalised children, Greece, 2008 to 2020: A prospective multicentre study

Background: Two rotavirus (RV) vaccines were licensed in Greece in late 2006 and included in the national immunisation programme in 2012. Aim: To study the epidemiology and genotype distribution of RV in children during the post-vaccination period and assess the impact of increased vaccination coverage. Methods: In a prospective multicentre hospital- based study, hospitalised children (<= 16 years) with an RV-positive faecal sample were recruited. Epidemiological and genotyping analyses were performed; periods of low (200812) and moderate (2012-20) RV vaccination coverage were compared. Statistical analysis was performed with a chi-squared or Mann-Whitney U test and logistic regression. Results: A total of 3,874 children (55.6% male; n = 2,153) with median age of 1.4 years (IQR: 0.5-3.3) were studied during 2008-20. Most RV- infected children were aged <= 3 years (72.2%) and hospitalised during December-May (69.1%). Common RV genotypes (G1P[8], G2P[4], G3P[8], G4P[8], G9P[8], G12P[8]) were detected in 92.2% of samples; G-P combinations with prevalence above 1% were G4P[8] (44.1%), G1P[8] (25.4%), G2P[4] (14.9%), G9P[8] ( 3.5%), G12P[8] (2.2%), G3P[8] (2.1%), other (4.3%) and mixed (3.5%). Of all samples, 97.6% were homotypic or partially heterotypic to vaccines' genotypes. With moderate vaccination coverage, the seasonal peak was detected earlier, children were older and partially or fully heterotypic genotypes were increased (p < 0.001). Conclusions: In the era of moderate RV vaccination coverage in Greece, epidemiology of RV in hospitalised children seemed to change. However, most circulating genotypes remain homotypic or partially heterotypic to RV vaccines. Continuous epidemiological surveillance and genotyping are important to monitor possible changes arising from RV vaccines' implementation.