Interruption of rubella virus transmission in Australia may require vaccination of adult males: evidence from a Victorian sero-survey.

Prior to the introduction of rubella vaccine to Australia in 1970 rubella was primarily a disease of primary school aged children. Vaccination programs have subsequently altered rubella age and sex susceptibility. Between July 2001 and June 2002, 85 per cent of the 32 laboratory-confirmed cases of rubella ascertained from enhanced surveillance in Victoria were males aged 20-42 years. This study aimed to determine rubella susceptibility by age group and sex in Victoria and to examine the implications of susceptibility for the interruption of circulating rubella virus. Rubella immunoglobulin G concentrations were determined for 934 residual diagnostic sera stored at the Victorian Infectious Diseases Reference Laboratory using a standard commercial enzyme immunoassay. Susceptibility was analysed by age groups defined by previous and current Australian rubella immunisation schedules. Among all subjects aged 1-55 years, males were more susceptible to rubella infection than females (10.2% vs 2.6%, p < 0.0001). Although this sex difference occurred in all age groups, it was unlikely to be explained by sampling variation in sera from subjects aged 23-44 years, for whom rubella vaccine had been recommended only for girls aged 10-14 years and rubella susceptible women post-partum. Australia's past rubella immunisation policies have resulted in a susceptible cohort of adult males. If rubella virus transmission is to be interrupted in Australia, consideration needs to be given to a rubella vaccination program targeting men aged 17-44 years. A campaign, targeting both men and women in a similar age group has recently been successful in Costa Rica.