Methods of assessing the impact of congenital rubella infection

Monitoring of congenital rubella infection (CRI) involves measuring the assessable outcomes of infection of the pregnant woman. These assessable outcomes are infection itself, therapeutic abortion, and birth of infants with congenital rubella syndrome (CRS). The incidence of infections can be estimated with use of data on age-specific occurrence of acquired rubella or acquisition of antibody in females and on fertility rates. The incidence of CRS can be estimated from data on infections of pregnant women and reports in the literature of incidence rates of CRS among infants born of infected mothers. Surveillance of CRS can involve individual case detection or serosurveys among populations with defects characteristic of CRS, such as deafness, and among comparison groups. To assess the impact of CRI, countries without rubella control programs should estimate the frequency of infections in pregnant women from existing surveillance data or determine by serosurveys the susceptibility and/or age-specific acquisition of rubella antibody in postpubertal females. Countries with rubella control programs should monitor cases of acquired rubella and/or prevalence of seropositivity in postpubertal females, therapeutic abortions, and CRS to assess effectiveness of the program and to determine high-risk populations that should be targets of intense vaccination programs.