Rubella immunity among prenatal women in Ontario, 2006–2010

BACKGROUND Countries of the Americas have been working towards rubella elimination since 2003 and endemic rubella virus transmission appears to have been interrupted since 2009. To contribute towards monitoring of rubella elimination, we assessed rubella seroprevalence among prenatal screening tests performed in Ontario. METHODS Specimens received for prenatal rubella serologic testing at the Public Health Ontario Laboratory, the provincial reference laboratory, between 2006 and 2010 were analyzed. A patient-based dataset was created using all tests occurring among 15-49 year-old females, where prenatal screening was indicated. Multiple tests were assigned to the same patient on the basis of health card number, name and date of birth. Only unique tests performed at least nine months apart were included. SAS version 9.2 was used for analysis. RESULTS Between 2006 and 2010, we identified 459,963 women who underwent 551,160 unique prenatal screening tests for rubella. Of these, 81.6%, 17.1% and 1.4% had one, two and three or more tests respectively. CONCLUSION Rubella susceptibility among prenatal women in Ontario supports elimination goals as population immunity in this group is relatively high. Higher susceptibility among young women and women living in the north highlights an opportunity for greater focus on identification and immunization of susceptible women in these groups.