The incidence and direct medical cost of hospitalization due to rotavirus gastroenteritis in Kyoto, Japan, as estimated from a retrospective hospital study.

Anticipating imminent licensure of rotavirus vaccine for use in Japan, we estimated the incidence of rotavirus hospitalization and calculated the direct medical cost associated with rotavirus hospitalization in a hospital that provided virtually exclusive pediatric beds to the local community adjacent to the northern outskirts of metropolitan Kyoto, Japan. For a 2 year period between September, 2008 and August, 2010, there were 103 hospitalizations due to acute gastroenteritis among children less than 5 years of age. Stool specimens from 77 (75%) of the 103 hospitalized patients were tested for rotavirus antigen, and 46 (60%) were positive. The proportion of rotavirus positives was 65% in the peak-season months (January-June) and 17% in the off-season months (July-December). By extrapolating the test results to those patients with acute gastroenteritis who were not tested, 13 additional cases were estimated to be rotavirus positive. Assuming that all patients with rotavirus gastroenteritis less than 5 years of age in the catchment (5532 according to the 2005 census) were admitted to this hospital, the annual incidence of rotavirus hospitalization was estimated to be 4.1 (testing-unadjusted)-5.3 (adjusted) per 1000 child-years. Thus, it was estimated that one child in 48 or one child in 37 born in this area would be hospitalized due to rotavirus gastroenteritis by the age of 5 years. The incidence of rotavirus hospitalization was similar to the rate in Ise city (4.9 per 1000 child-years), also in central Japan, and lower than the rate in Honjo city in northern Japan (13 per 1000 child-years). Nevertheless, the burden of rotavirus hospitalization was substantial, and the total direct medical cost was estimated to be 6.6 billion Japanese Yen (US$ 57 million). While economic analysis and comparisons with alternative preventive procedures may be necessary, this study provides the policymakers and pediatricians with further evidence that is necessary to decide whether to introduce rotavirus vaccines into the routine childhood immunization schedule in Japan.