Exploring the implications of changing patterns of rubella immunity in antenatal women in a South Wales valley community

• Main Author: Matthews, L. A.
• Published: University of the West of England, Bristol 2013
• Subjects: 610.28
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589116

Background/Aims: Rubella can be devastating to a foetus if maternally acquired in early pregnancy. A single rubella vaccine (SRV), given to prepubertal girls was replaced by the MMR immunisation in infancy for both sexes in 1988. Women born before 1983 probably received the SRV and had contact with circulating rubella, whilst women born after 1982 probably received the MMR vaccine and had little contact with circulating rubella. When immunity levels fall, outbreaks can occur, as seen in the last 10 years. The rubella status of antenatal women in the Cwm Taf (South) Health Board area and post-partum vaccine uptake in the rubella susceptible women was explored. Method: Data of 14,519 antenatal rubella tests (2005-2010) and questionnaire data from 111 rubella susceptible women (2009-2011) were analysed. Self-reported immunisation status and post-partum vaccine uptake were validated by examination of childhood immunisation records and medical records. Data for probable SRV recipients and probable MMR vaccine recipients were compared. Key Results: The overall rubella susceptibility rate increased from 3.8% (88/2312) in 2005 to 4.6% (116/2536) in 2010. First pregnancy data showed a statistically significant increase in susceptibility from 6.4% (49/760) in 2005 to 8.9% (71/798) in 2010 (c²=6.860, df=1, p=0.009) and women born after 1982 were five times more likely to be rubella susceptible than those born earlier (odds ratio=5.05, 95% CI from 3.46 to 7.35). Those aged < 20 years had a mean susceptibility rate of 21.3% (236/1107) Average antibody titres for rubella immune women differed significantly by year of birth; those born earlier had a stable average of 58 IU/ml whilst those born later (following a period of steady decline) averaged 20 IU/ml. Of rubella susceptible women in the questionnaire study, 62.8% had received two or more doses of a rubella containing vaccine. Examination of medical records showed that over 36% (39/107) of rubella susceptible women in the study did not receive post-partum immunisation. Conclusion: The results suggest that immunity is waning, and that a third dose of MMR vaccine in adolescence is required to ensure protection during pregnancy. The study also demonstrates that reliance on Child Health Records to assess need for immunisation is flawed. Post-partum MMR uptake also needs to be addressed if national targets are to be met.