Many directly transmitted diseases present a strong age dependent pattern of infection. Such dependency is analyzed by a mathematical model encompassing an age-structured pattern of contacts. From an age-structured contact rate modeling, we estimate the parameters related to the contact rate based on the age dependent force of infection calculated from a seroprevalence data obtained from a nonimmunized population. This model, with parameters completely determined, is used to assess the effects of vaccination strategies. This is done by calculating the new equilibrium age dependent force of infection and its correlated variables: the average age of the acquisition of the first infection, the rate of new cases of infection, and the risk of Congenital Rubella Syndrome. Also, we present a rough estimation of the basic reproduction ratio and the vaccination rate at which the disease can be considered eradicated (threshold). (C) 1999 Elsevier Science Ltd. Ail rights reserved.2971130