Two new studies have shed light on how altering breast-feeding practices and drug delivery could help reduce the rate of mother-to-child HIV transmission in poor nations. Experts say the new results will have serious implications for future updates to policy guidelines on HIV and infant feeding by the World Health Organization (WHO).

“These are very important studies that have been very well conducted,” says Anirban Chatterjee, a nutrition specialist at UNICEF who sits on the committee responsible for the WHO's HIV and infant feeding guidelines.

In sub-Saharan Africa, about 1.5 million pregnant women live with HIV. Without antiretroviral drug treatments, the likelihood that these women will pass on the virus to their child if they breast-feed—which most do for at least a year and a half—is perhaps as high as 45%, according to estimates from the WHO.

No simple formula: Breastfeeding carries risks Credit: PhotoTake

Because of this risk, babies born to women with HIV in Western countries are fed only formula to prevent viral transmission through breast milk. But this isn't an option in poor countries. Not only is formula expensive, but making it safely requires refrigeration and clean water. Moreover, children who are not breast-fed miss out on the enormous immunological benefits from the milk. They therefore have a much greater chance of dying from pneumonia, diarrhea or malnutrition.

“The main challenge is how can we make this breast-feeding period safe?” says epidemiologist Taha Taha of Johns Hopkins University in Baltimore.

A study led by Taha involving more than 3,000 infants in Malawi found that an extended regimen of the inexpensive antiretroviral drug nevirapine to infants during the first 14 weeks of breast-feeding significantly reduced the number of HIV infections recorded in the infants up until they reached nine months.

In most clinics within sub-Saharan Africa, a baby born to an HIV-positive mother will receive a single dose of nevirapine at birth. In Taha's new Malawi study, a control group of infants was given a single dose of nevirapine, while another group was given nevirapine daily until they were 14 weeks old.

At nine months, the infants given the extended nevirapine treatment had an HIV-infection rate of 5.2%, as compared with 10.6% of the control group (N. Engl. J. Med., doi:10.1056/NEJMoa0801941; 2008).

A second study involving nearly 1,000 HIV-positive mothers in Zambia found that abrupt weaning—a common practice previously recommended by the WHO—did not improve survival rates of babies who were not infected with HIV, and actually increased the mortality rates of babies who were infected with HIV (N. Engl. J. Med., doi:10.1056/NEJMoa073788; 2008).

The WHO's current HIV and Infant Feeding guidelines were originally released in 1998, and updated in fall 2006 with preliminary data from this newly published study of abrupt weaning. For regions where safe formula-feeding is not available, the new guidelines recommend that HIV-positive mothers breast-feed exclusively up to six months and then continue to breast-feed while gradually introducing other foods.

It might be a long time, however, before these official updates trickle down to individual clinics. Despite the risk of bacterial contamination, formula feeding continues in some poor countries as part of a legacy from health recommendations issued in the early 1990s.