Transmission of hepatitis A through household contact

In the USA, cost effectiveness assessments support childhood hepatitis A va ccination in geographical areas with elevated disease rates, but not nation ally. However, these studies do not address the reduction in disease transm ission which may result from routine childhood vaccination. Using decision analysis, we estimated the number and age distribution of secondary hepatit is A cases occurring within households with an index case. Based on the age of the index case, we determined household size and age composition, the p roportion of household members susceptible to hepatitis A, the probability of disease transmission, and the likelihood secondarily infected household members would exhibit symptoms. Our model indicates that for every 100 inde x cases age 6-11 years, 47.2 secondary infections would occur within househ olds, with 23.1 causing overt disease. Lower transmission rates for older i ndex cases reflect smaller household sizes and a higher proportion of house hold contacts with hepatitis A immunity. When disease transmission rates ar e applied to a model simulating lifetime risks of hepatitis A, universal va ccination of an annual USA birth cohort is estimated to prevent 24100 cases of overt disease among household contacts in addition to 71000 cases among vaccinees. Sensitivity analysis provides a wide range of estimates, but ev en conservative assumptions suggest routine vaccination would yield an impo rtant reduction in secondary cases. Evaluations of hepatitis A prevention s hould consider the ability of immunization to protect household and other p ersonal contacts.