Irish Medical Journal Press Release
September 2013 ■ Volume 106 ■ Number 8
Official Journal of the Irish Medical Organisation
Antenatal Rubella Immunity in Ireland

A new study in the September edition of the Irish Medical Journal analyses antenatal rubella immunity in Ireland in 2009. The objective of the study carried out by O’Dwyer and her colleagues in the UCD Centre at the Coombe and the ESRI was to identify the demography of women booking for antenatal care in Ireland who were rubella seronegative, and to identify those women who may have benefited from prepregnancy vaccination. This comprehensive national study shows that the percentage of pregnant women in Ireland with immunity to rubella in 2009 was less than the WHO target of 95%.

In Ireland, women are routinely screened for rubella immunity at their first antenatal visit. Protective immunity is defined as ≥10 IU/ml. After delivery rubella immunity is coded as immune, not immune or unknown/not stated. Women who are not immune are offered rubella vaccination post-partum.
Rubella is usually a mild febrile illness of little significance in children and adult males. About half the infections are subclinical and complications such as encephalitis and haemorrhagic manifestations are rare. Rubella infection in pregnancy, however, is of major public health importance because it is teratogenic in the non-immune woman. The infection may result in miscarriage, foetal death or birth of an infant with congenital rubella syndrome (CRS)

The spectrum of CRS depends on the gestational age at the time of infection. During the first trimester up to 85% of infants infected will develop CRS which may result in deafness, cataracts, heart defects, microcephaly, developmental delay, bone changes and hepatosplenic damage. CRS is rare when infection occurs after 20 weeks gestation. CRS is also important because it is preventable by vaccination

The woman’s age, parity, nationality and rubella immunity status were analysed using data collected by the National Perinatal Reporting System. The findings of the study revealed that the data collected from 74,810 women, the rubella status was known in 96.7%. Of the 72,337 women where the rubella status was known, 6.4% were non-immune. In women where the rubella immune status was known, 8.0% of 30,331 primiparous women were seronegative compared with 5.3% of 42,002 multiparous women.

The authors analysed the nationality groups according to whether they were <25 years of age or over 25 years. In 10,653 women <25 years, 14.7% were seronegative compared with 5.0% of the 61,663 women ≥25 years. Demographic analysis showed that the women who were most at risk of rubella infection were younger women, first-time mothers and women with a nationality from outside the 27 EU countries.

In 2005, the World Health Organization (WHO) Regional Committee for Europe endorsed combined measles and rubella vaccine programmes which aimed to prevent CRS (<1 case per 100,000 live births) by 2010. The evidence from this study suggests that this goal was not met.

A rubella vaccination programme for girls between their 12th-14th birthdays was introduced in 1971. The Measles, Mumps, Rubella (MMR) vaccine was introduced in 1988 for all children at the age of 15 months to two years and for females aged 10-14 years. A second dose of MMR was introduced for all children in 1992. In 1999 the age for the second dose of MMR was dropped from 10- 14 years to 4-5 years of age. CRS as a distinct entity only became notifiable in 2004. By 2005, the incidence of rubella was 0.4/100,000 (17 cases) and there were no cases of CRS. The last case was reported in 2004, in contrast to 106 cases of CRS reported between 1975-1990.

The high rate of rubella seronegativity in women <25 years of age is of concern to the authors. This may be related to the low percentage uptake of Measles, Mumps and Rubella (MMR) a decade ago in response to misguided parental concerns about the risks of vaccination. More recently, immunisation coverage has improved but the 2007 National Report on preventing CRS recommended that routine immunisation activities need to be strengthened to ensure that at least 95% of children receive two doses of MMR.

Women coming from non-EU countries, where rubella vaccination was not standard, were more likely to be non-immune to rubella. “Focusing on this easily identifiable group for screening and vaccination prepregnancy would be cost-effective. It may also be more cost efficient to vaccinate without serological testing women from countries without rubella programmes. “state the authors.

The authors also note that immigrants into Ireland after 4-5 years of age may be missed by current vaccination programme; they recommend that this vulnerable group should ideally be screened before or shortly after arrival in all EU countries. “Such a policy should also improve rubella herd immunity and help meet the renewed WHO European regional goal.” say the authors. “Based on the findings we recommend that to prevent Congenital Rubella Syndrome, the health services in Ireland should focus on women who are young, nulliparous and born outside the EU.”

All references and author names are contained in the full article in this month’s IMJ, p.232
Title: Antenatal Rubella Immunity in Ireland