A new treatment for infants of HIV-positive mothers could prevent hundreds of thousands of infections a year in the developing world, according to a report in today's New England Journal of Medicine.
The study by researchers at the Johns Hopkins Bloomberg School of Public Health tested whether an extended regimen of anti-AIDS drugs could protect infants from becoming infected by their mothers' breast milk.
The treatment cut transmission of HIV from mothers to infants by 50 percent.
"This is a landmark study," said Charles van der Horst, an AIDS researcher at the University of North Carolina. "The treatment had an extraordinary effect."
Every year, 500,000 babies are infected with HIV by their mothers. Half of those infections occur through breastfeeding. In the West, infants of HIV-positive mothers are almost always fed formula, and, in part because of this practice, rates of mother-to-child transmission have dropped to less than 1 percent.
But in the developing world, this approach is untenable. Many families can't afford formula, and even if they can, they often lack access to clean water.
"Breast milk is nutritionally very convenient," said Dr. Taha Taha, a Johns Hopkins epidemiologist and lead author of the study.
Many studies have shown that breastfeeding increases overall infant survival rates, even when the mother has HIV. Breast milk increases immune function and reduces the severity of diarrhea and pneumonia, two major killers of infants in poor countries.
"Breastfeeding is essential for at least the first six months, even in HIV-positive mothers," said UNC's van der Horst.
In recent years, researchers have tested a variety of methods to minimize the risk of HIV transmission through breast milk. Before that, he said, researchers largely ignored the issue.
"It's a unique problem for resource-poor countries because HIV-positive mothers don't breastfeed in the West," he said.
In the developing world, most infants of HIV-positive mothers currently receive one dose of nevirapine, an anti-HIV medicine, soon after birth.
The new study, which took place in Malawi, extended that regimen. The researchers divided 3,016 breastfeeding infants into three groups: In one group babies got a single dose of nevirapine; in another they got nevirapine for 14 weeks; the third got nevirapine and zidovudine, another antiretroviral drug, for 14 weeks.
In the latter two groups, HIV rates dropped by half. In addition, infants showed no ill effects from the longer drug treatments.
HIV is a significant problem in Malawi, one of the world's poorest countries. Sixteen percent of its 12 million inhabitants are HIV-positive. The country also has a high child mortality rate: One of every five children dies before the age of 5. In this context, experts say, breastfeeding is crucial.
The researchers said the study provided strong evidence for the longer treatment regimen.
"The study has a big sample size, so the data is really strong," said pediatrician Mary Glenn Fowler, a Johns Hopkins HIV researcher in Kampala, Uganda, and a co-author of the study.
Taha said researchers and public health officials are devising plans to roll out the new treatment in Malawi and elsewhere. Taha is working with the Malawian government and is part of a World Health Organization panel dealing with the issue.
In much of sub-Saharan Africa, the cost of nevirapine and zidovudine is subsidized by international aid, including the U.S. government's $15 billion AIDS program, and the Global Fund to Fight AIDS, Tuberculosis and Malaria. As a result, poor countries such as Malawi might end up not paying much to extend treatment to all infants of HIV-positive mothers.
The treatment itself is simple: Using a dropper, mothers give their babies the medicine in a syrup.
Even so, setting up widespread programs, particularly on a continent that remains largely rural, will be difficult. "The cost is not the major barrier," Taha said. "The logistical barriers will be key."
Dr. Brooks Jackson, an AIDS expert at the Bloomberg School of Public Health, agreed that implementing the treatment would be difficult. Jackson, who was not involved in the study, noted that 30 percent of pregnant HIV-positive women in Africa still do not get a dose of nevirapine during labor. That therapy was proved nine years ago to reduce HIV transmission by half.
Scientists are testing other treatments to further reduce mother-to-child transmission of AIDS. Taha and Jackson are now planning a trial in several African countries in which infants take antiretroviral drugs for six months or longer.
In Malawi, van der Horst is examining whether giving anti-HIV medicine to nursing mothers with the disease can reduce transmission.
"In the U.S., we've largely stopped mother-to-child transmission," said van der Horst. "We can do the same in the developing world."