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

Objectives: To 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 (R) vaccine, and to examine the vaccine effect on circulating genotypes. Methods: Since 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. Results: RV 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 GIP[8], emergence of G9P[8] and especially more recently GI2P[8]. In the elderly, G2P[4] was predominant but was also replaced by GI2P[8] in 2017-18. Conclusions: RV 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 GIP[8]. Increase of overall RV activity with emergence of GI2P[8] in the latest follow-up season 2017-18 might be a potential alarm sign. (C) 2019 The British Infection Association. Published by Elsevier Ltd. All rights reserved.