The impact of rubella immunisation on the incidence of rubella, congenital rubella syndrome and rubella‐related terminations of pregnancy in South Australia

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Abstract
Objectives To describe the impact of rubella immunisation on the incidence of rubella, congenital rubella syndrome and rubella‐related terminations of pregnancy in South Australia, and to identify factors associated with a re‐emerging problem. Design and Methods A population‐based descriptive study using data from South Australian notifications of disease, births and terminations of pregnancy, the rubella immunisation programme, antenatal rubella antibody screening and paediatric hospital case records. Setting South Australia (population 1.48 million people; 20,000 births per year). Main outcome measures Incidence of rubella (age‐sex specific), congenital rubella syndrome and rubella‐related terminations of pregnancy; antenatal rubella sero‐positive rates; rubella immunisation uptake rates. Results Rubella notification rates in 1990–1996 were significantly higher for males than females for ages 15–34 years. There were five cases of congenital rubella syndrome notified in 1980–1996 compared with at least 20 confirmed or compatible cases in 1965–1979. Rubella‐related terminations of pregnancy are now rare, with the last termination for maternal rubella being in 1993. The antenatal rubella sero‐positive rate in 1995 was 96.7%, but was significantly lower among Asian women born overseas (78.6% among those 30 years or older). Vaccination uptake rates in schoolgirls decreased between 1990 and 1994 (91.2% to 86.9%). Conclusions Since the introduction of rubella immunisation, the incidence of rubella infection among women of reproductive age, and of rubella‐related terminations, has fallen. Congenital rubella syndrome has not been notified since 1990 but its risk persists with a recent increase in rubella notifications, a fall in school immunisation rates, a relatively low antenatal sero‐positive rate among older Asian women born overseas and the trend towards giving birth at older ages. Effective immunisation programmes must be maintained, particularly in schools and for young children and migrant women.