The incidence of Kawasaki syndrome in West Coast health maintenance organizations

Background. Kawasaki syndrome (KS) causes an acute vasculitis of unknown et iology. It is a leading cause of acquired heart disease of children in Japa n and the United States. Methods, We examined the incidence of KS in a well-defined population group of children less than or equal to 6 years of age, using data collected thr ough the Vaccine Safety Datalink (VSD) project. The VSD database contains i nformation on >1 million children enrolled in four West Coast health mainte nance organizations (HMOs). Results. During 1993 through 1996 a total of 234 physician-diagnosed KS pat ients were reported in the 4 HMOs; 152 (65.0%) were boys and 195 (83.3%) we re <5 years of age. The incidence of KS among children <5 years of age in t he HMOs ranged from 9.0 to 19.1 per 100 000 person years. KS incidence was higher among boys in 3 of the sites. In the 2 sites with the highest number of KS patients, a seasonal occurrence of KS in winter and early spring was observed. Overall 226 (96.6%) of the KS patients were reported to have bee n hospitalized; hospitalization rates for children <5 years of age ranged f rom 9.0 to 16.8 per 100 000 person years. Conclusions. The incidence of KS in the HMOs as similar to that reported in other population-based studies in the United States and higher than estima tes for Australia and several European countries.