Rash of rubella on skin of child's back, CDC.

Many thousands of women in developing countries, unvaccinated against rubella and unaware of the risks of infection, contract the virus during pregnancy and give birth to children with congenital rubella syndrome. Estimates suggest that around 100,000 babies are born every year with the syndrome, which includes mental retardation, heart disease, cataracts and deafness.

Now aid agencies plan a mass immunisation program with combined rubella and measles vaccines, says Stanley Plotkin, the virologist who developed the rubella vaccine.

"It is being recognized as a public health problem, but the information from the developing world is relatively scant. But where you look for it, you find it", Plotkin told BioMedNet News.

Exposure to the virus tends to occur during childhood, which usually provides protection against a second infection in adulthood, including during pregnancy. But some communities, particularly in island populations, may go for some time without experiencing the disease.

As many as half the women in these communities can have missed childhood exposure, estimates Plotkin. "These are places where the introduction of rubella virus could be catastrophic," he said.

In response, the Pan American Health Organization (PAHO) and the US March of Dimes Foundation accept that adding the rubella vaccine to the more widely distributed measles vaccine would improve immunization, Plotkin claims. The American Red Cross is also considering the same move, he adds.

Until now, however, the World Health Organization (WHO) and others have resisted mass vaccination initiatives, notes Plotkin. "There's at least a theoretical problem in incomplete vaccination: if you dribble vaccine in there's a risk of decreasing recirculation and rendering more adult women susceptible," he said.

The answer lies in the scale of the program. If it achieves more than 80% coverage, the risk of an increase in congenital rubella syndrome goes down, says Plotkin. He would like to see universal immunization with the triple childhood vaccine for mumps, measles and rubella (MMR).

The real problem, says Plotkin, is attitude. "There is a certain amount of conservatism in public health," he noted. "I guess it's the old maxim about doing no harm, but that can result in status quo and stasis".

A second obstacle is cost, but using MMR rather than developing a totally new vaccine would help, says Plotkin. "The issue of price always comes up - since an effort is being made through the Gates Foundation to bring in routine vaccines, MMR should be one of them," Plotkin told BioMedNet News.

Eight companies now produce MMR vaccines, including Aventis Pasteur, for whom Plokin is the medical and scientific adviser. Ironically, he notes, if demand were suddenly to rise, there could be a transient supply problem.

"Supply is a circular problem: as long as there's not a perceived demand there's no incentive for companies to increase their supply, but it could be increased," Plotkin concluded.