Rubella-vaccination programmes account for the increasing rarity of congenital rubella syndrome (CRS) in many parts of the industrialised world, particularly Britain, Scandinavia, and North America.

In many industrialised countries vaccination has generally been directed towards 1-2-year-old children as well as women of childbearing age. Is it now time to focus attention on developing countries? There, the degree of susceptibility among women of childbearing age may not always have been appreciated. The burden induced by CRS, which may also impose a considerable strain on scarce health and educational resources, may also be insufficiently recognised.

WHO has recently published important studies that should set the stage for rubella-immunisation programmes in developing countries. Data from 45 developing countries showed that, despite considerable variation even within different parts of a country, in many nations the proportion of rubella-susceptible women (15-20%) is similar to that in industrialised countries in the prevaccination era. Susceptibility rates of less than 10% were reported for 13 countries, 10-24% for 20, and more than 25% for 12. Some countries had appreciably higher susceptibility rates before the introduction of vaccination programmes-eg, Trinidad and Tobago (68%) and Thailand (30%). The high prevalence of rubella antibodies among pregnant women may reflect recent unrecognised epidemics; infection may have been atypical or subclinical, or rubella-induced rashes may have been misdiagosed.

Studies conducted after outbreaks of rubella in the Middle East, Central America, the Caribbean, and South- east Asia through the 1970s to the 1990s showed that the incidence of CRS per 1000 livebirths was usually much higher (range 0.6-2.2 per 1000 livebirths) than in the UK during the early years of its rubella-vaccination programme (0.14 per 1000 during epidemics; 0.08 at other times). An estimate derived from mathematical models for five WHO regions (excluding Europe) during 1998 suggested that there was somewhere of the order of 236000 cases of CRS in developing countries during non-epidemic years but that this number might increase ten-fold during epidemics. Even this figure may be an underestimate since infants were usually assessed shortly after birth or during early infancy, commonly before such manifestations of CRS as deafness were evident.

Appropriate WHO leadership should give impetus for more developing countries to conduct local epidemiological and virological surveillance. As surveillance improves for measles elimination, a WHO network of diagnostic laboratories for rash-associated illness will probably be established, as has been done for diagnosis of poliomyelitis. Such laboratory support should offer the capability for the diagosis of measles and rubella, as well as of CRS. For CRS, new diagnostic tests are promising. Although CRS is usually diagosed by the detection of rubella-specific IgM in serum, which persists until the age of 6-9 months, salivary IgM antibody responses are similar to serum responses and have been shown to be useful in studies done in India.Laboratory diagnosis is more difficult in older children, although case-control comparisons of rubella IgG prevalence among children with hearing and eye defects may be useful epidemiologically. More recently, rubella virus has been identified in Indian children by PCR on lens aspirates from surgically removed cataracts. Although such investigations can be undertaken only in specialist centres, the technique may be useful in older children because rubella may be recovered from cataracts from children with CRS up to 3 years of age. Only 28% of developing countries are implementing national rubella-vaccination programmes. Unfortunately, some are unlikely to reduce the incidence of CRS for many years since vaccination is directed towards children, sometimes selectively at schoolgirls. Women of childbearing age are not being vaccinated systematically. To reduce CRS rapidly, both groups should be targeted. In fact, every opportunity should be taken to vaccinate women of childbearing age, especially post partum. Programme costs can be reduced by dispensing with antibody screening. Although some women may already be pregnant, or become so within a month of vaccination, the accumulated data from several national programmes are sufficiently convincing to provide firm reassurance that the vaccine is most unlikely to induce fetal damage.

An ideal opportunity to implement rubella-vaccination programmes exists because, globally, measles-vaccination- uptake rates average about 80% or more, and some regions have adopted measles-elimination goals. In countries with sustained measles coverage of at least 80%, a single dose of a combined measles and rubella vaccine should be given to all children, preferably at age 1-2 years. Selective programmes will not interrupt virus transmission to susceptible pregnant women. However, countries with relatively low (about 60%) measles-vaccine-uptake rates-eg, parts of Africa-would be unwise to introduce rubella vaccination until measles-vaccine-uptake rates have improved, since intermediate vaccination rates may increase the average age of infection and, consequently, the incidence of CRS. Furthermore, it must be appreciated that the poorest countries have, apart from the problem of low coverage, other competing priorities. Nevertheless, huge strides have been taken with prevention of measles and poliomyelitis. With rubella there is room for improvement.

Last updated Jan 4/07