Continuing rotavirus circulation in children and adults despite high coverage rotavirus vaccination in Finland

Abstract

ObjectivesTo determine occurrence of residual rotavirus (RV) disease in different age groups in Finland after five to nine years of high coverage (≥90%) mass-vaccination with RotaTeqⓇ vaccine, and to examine the vaccine effect on circulating genotypes. MethodsSince 2013 all clinical laboratories in the country were obliged to send RV positive stool samples for typing. RVs were genotyped by RT-PCR for VP7 and VP4 proteins, sequenced and compared to reference strains. ResultsRV continued to circulate throughout the study period at low level with a small increase in 2017–2018. There were three age-related clusters: young children representing primary or secondary vaccine failures, school-age children who may not have been vaccinated, and the elderly. Genotype distribution differed from the pre-vaccination period with a steady decline of G1P[8], emergence of G9P[8] and especially more recently G12P[8]. In the elderly, G2P[4] was predominant but was also replaced by G12P[8] in 2017–18. ConclusionsRV vaccination with a high coverage keeps RV disease at low level but does not prevent RV circulation. New RV genotypes have emerged replacing largely the previously predominant G1P[8]. Increase of overall RV activity with emergence of G12P[8] in the latest follow-up season 2017–18 might be a potential alarm sign.