Theoretical aspects of rubella vaccination strategies.

The theoretical epidemiologic basis for an appropriate vaccination strategy for the prevention of congenital rubella syndrome is outlined and reviewed. The main choice lies between a direct strategy, in which adolescent girls and women are protected against the effects of being exposed, and an indirect strategy, in which children of both sexes are vaccinated and in which women are protected through the interruption of rubella transmission and are not exposed at all. The direct strategy produces a slow response but is free from substantial hazard. The indirect strategy produces a more rapid response but carries hazards, which arise from either shortfall in uptake, decay of vaccine-induced immunity, or from combinations of the two. In unfavorable circumstances, an indirect strategy produces paradoxical responses that increase rather than decrease the incidence of congenital rubella syndrome either immediately or as a "rebound phenomenon" after some years. A rational choice of policy depends chiefly on the transmission rate in the population concerned and on an estimate of the achievable level of uptake.