Scientists fighting the ravages of AIDS in the Third World have shown convincingly that a short and relatively inexpensive combination of HIV drugs could reduce mother-to-baby transmission rates in Africa far more effectively than the single pill now used.
But the cost of the drug combinations could still be prohibitive in some of the most impoverished parts of the world.
Scientists have long been searching for an alternative to the AIDS drug now widely used in the Third World, nevirapine. Nevarapine (search) is cheap and highly effective at preventing babies from contracting the AIDS virus from their mothers. But up to two-thirds of women become resistant to the drug.
The drug combinations appear to have an extremely low rate of resistance, and offer a relatively inexpensive and easy-to-take alternative for many women.
"This is very promising for low-income countries," said one of the researchers, Dr. Francois Dabis of Victor Segalen University in Bordeaux, France.
However, the drug combination would likely cost more than double the usual $8 for a single dose of nevirapine for mother and newborn. As it is now, some countries cannot even afford nevirapine.
"It's important not to be rapidly overoptimistic," said Dr. Mary Fowler, a U.S. Centers for Disease Control and Prevention specialist in mother-to-baby HIV transmission. "The translation from trials to programs is incredibly challenging."
The findings were presented in Boston on Thursday at the 12th Annual Retrovirus Conference, the world's chief scientific meeting on AIDS.
In impoverished lands, nevirapine is widely given in single doses to infected pregnant women in labor and then to their newborns.
In the United States, the complete three-drug HIV cocktail has cut mother-to-baby transmission rates to around 2 percent. But patients in the United States are given longer treatments, and drugs that are far more effective and expensive than those tested in Africa.
The African studies — one in the Ivory Coast, one in Botswana — reduced rates at four to six weeks after birth to about 5 percent, the lowest ever recorded in Africa. Nevirapine in single doses typically reduces that rate from around 35 percent to 12 percent.
In the Ivory Coast study, French and African-based researchers used single-dose nevirapine in 329 women, but coupled it with two other common AIDS drugs: AZT (search) and 3TC (search), sold collectively as Combivir (search). The Combivir was given to the mothers during pregnancy and for three days after birth. The newborns were also given single-dose nevirapine and AZT.
At six weeks of age, fewer than 5 percent of the newborns were infected. Drug resistance was also extraordinarily low in the mothers. Only 1 percent became resistant to nevirapine, and just 8 percent to 3TC.
In the Botswana study of 1,179 births, mothers were given multi-week AZT alone, and in combination with single-dose nevirapine.
The World Health Organization is expected to consider broadening its guidelines soon in light of research on such new regimens. Its recommendations now include single-dose nevirapine and an AZT-nevirapine regimen.
"For a minimum additional cost, we may get many benefits," said Dr. James McIntyre, an AIDS researcher in South Africa.
However, several researchers cautioned that single-dose nevirapine will still be needed in many places.
"It is essential to preserve single-dose nevirapine as an option when more complex regimens are unavailable," said Mark Isaac, vice president of policy at the Elizabeth Glaser Pediatric AIDS Foundation in Washington.
A separate arm of the Botswana study also gave a boost to advocates of breast feeding for HIV-infected women. Some babies were breast-fed and treated with AZT for six months, while others were given formula. More of the first group contracted HIV, as expected, since the virus can be passed through breast milk. However, the two groups had almost identical rates of HIV-free survival after 18 months.
Doctors have long known that the AIDS virus can be transmitted through breast milk. But many are reluctant to discourage breast-feeding in the Third World, since formula feeding has been linked in the past to more baby illnesses and deaths from a variety of causes.
About 40 million people worldwide are infected with HIV. About 65 percent live in sub-Saharan Africa. About 3 million people died in the epidemic last year.