Effect of rotavirus vaccine on Sapporo virus gastroenteritis in Finnish infants

Background. Sapporo-like viruses (SLVs) occur worldwide, but there is limit ed information about the SLV-associated gastroenteritis outside Japan. Methods. Stool specimens from 1432 episodes of gastroenteritis that occurre d in children between 2 months and 2 years of age during a rotavirus vaccin e trial (776 episodes in placebo-vaccinated and 656 in rotavirus-vaccinated infants) were examined for SLVs using a reverse transcription-PCR assay. T he reverse transcription-PCR took advantage of new primers specific for Sap poro virus genetic clusters I, II and III; SV/SV82 (SV/Sapporo virus 82); S V/Lond92 (SV/London 92); and SV/PV (Parkville virus). Results. SLVs were detected in association with 132 (9.2%) of all episodes; in 80 (5.6%) episodes SLV was the only gastroenteritis virus detected. The epidemic season of SLVs peaked from March to May concurrently with rotavir uses and astroviruses and overlapping with Norwalk-like viruses. Clinically SLV gastroenteritis was characterized by a mild diarrheal disease, being s harply different from the Norwalk-like virus-associated "winter vomiting di sease." Rotavirus vaccination did not have any effect on the number of SLV episodes, but the intensity and duration of SLV-associated diarrhea were re duced in rotavirus-vaccinated children compared with placebo-vaccinated chi ldren (P = 0.0008). Conclusions. SLVs are common causative agents of acute gastroenteritis in y oung Finnish children. SLV disease is characterized by diarrhea, which is u sually mild but can be severe. By an unknown mechanism rotavirus vaccine se ems to reduce the severity of SLV-associated diarrhea.