New York, Jun 3 (IANS): Immunising mothers against flu can decrease the risk of their infants getting influenza during the first four months after birth by 70 percent, a study says.

"These results are an important early step toward implementing maternal immunisation against influenza to protect young infants, and the results are impressively positive," said senior author Myron Levine, Professor at the University of Maryland School of Medicine in the US.

Immunising pregnant women against the flu is common in the industrialised world, but not in the developing world.

This study, published in the journal Lancet Infectious Diseases, shows that such immunisation can work in the developing world too.

The research took place in Bamako, Mali, in West Africa.

The researchers studied 4,193 pregnant women. About half of the participants received a flu vaccine and the other half received a vaccine for meningitis.

The scientists followed the women's infants for six months after birth. In the group whose mothers had been vaccinated against flu, vaccine efficacy was nearly 70 per cent in the first four months after birth.

This fell to 57 per cent by five months, and disappeared by six months.

Vaccine efficacy refers to the percentage of reduction in disease incidence in a vaccinated group compared to an unvaccinated group.

In other words, in the flu vaccine group, in the first four months after birth, there were nearly 70 per cent fewer cases of flu than in the meningitis vaccine group.

The finding could help to significantly reduce flu disease and mortality in poor and developing countries.

Each year, influenza causes between 250,000 and half a million deaths around the world. Pregnant women and young infants have a higher risk of complications related to influenza and these complications can easily lead to death.

The problem is particularly severe in the developing world, where access to health care is often limited, and health centres and hospitals are scarce and under-resourced.

Babies are particularly vulnerable because there is no influenza vaccine approved for infants younger than six months.