Waiting to take 2d dose of AIDS drug may be key step

WASHINGTON -- A Harvard study has found a way around one of the thorniest problems in preventing HIV transmission from mother to child during birth in poor countries.

In recent years, efforts to prevent transmission of the deadly virus that causes AIDS were set back by the discovery that many mothers who received a single dose of the drug nevirapine during labor developed a resistance to it, foreclosing the chance to use the drug later to fight AIDS in their bodies.

But the study, which is being published today in The New England Journal of Medicine, found that if the mother waited six months after birth to take a nevirapine-based, antiretroviral treatment, resistance from that single dose during labor had vanished in the vast majority of cases.

The findings should give greater confidence to many governments in Africa to promote use of nevirapine at birth, which cuts the chances of transmission to babies by nearly 50 percent, researchers and a US policymaker said.

"If you can hold off on treatment for six months, if it's safe to, hold off," said Shahin Lockman , the lead author of the report and an assistant professor at the Harvard School of Public Health.

If the woman needs AIDS treatment after giving birth, Lockman's advice is to "do your best to get her on non-nevirapine based treatment."

Other studies have found that of the pregnant women who receive a dose of nevirapine at birth, a nevirapine-based treatment afterward is not effective in between 20 and 69 percent of them. The highest rates of resistance have been found in sub-Saharan Africa, the epicenter of the AIDS pandemic. Around the world, roughly 40 million people are now infected with HIV or have full-blown AIDS.

Thomas A. Kenyon , principal deputy coordinator for the US global AIDS program, a $15 billion, five-year effort to fight the virus, said the issue of resistances developing during anti-retroviral treatment needs to be monitored closely in the coming years.

"But what this [study] does provide is reassurance in the vast majority of instances, we're not creating a new problem of resistance by introducing single-dose nevirapine," Kenyon said.

The study began in 2001 and was based in Botswana, where Harvard AIDS researchers have long worked. The study followed 218 HIV-infected women who had received a single dose of nevirapine during labor as well as a short treatment of anti-retroviral drugs during pregnancy. Sixty women started a nevirapine-based treatment within six months of giving birth, while the remainder, 158, started on the drugs six months afterward.

The outcomes were dramatically different. Of those taking the drugs soon after birth, 41 percent experienced treatment failure. Of those who waited, just 12 percent had the treatment fail.

Shahin speculated the better results were because the amount of nevirapine-resistant HIV in the body decreases as time passes.

The best-known way to prevent mother-to-child transmission is to put HIV-positive pregnant women on anti-retroviral treatment during pregnancy; during labor, a single dose of nevirapine also can be given. In the United States, other rich countries, and some parts of the developing world, including Thailand, the Ivory Coast, and South Africa, healthcare workers have used this technique to lower the risk of transmission to between 1 and 4 percent.

But in sub-Saharan Africa, just an estimated 10 percent of HIV-infected pregnant mothers receive any type of intervention to prevent transmission of the virus. In the cases in which drugs are available, nevirapine during labor is often the only intervention. Researchers estimate that more than 875,000 women and infants in poor countries have received single-dose nevirapine at birth.

Max Essex , chair of the Harvard School of Public Health AIDS Initiative and one of the authors of the study, said doctors, nurses, and community health workers should use common sense when they oversee women who have just given birth. World Health Organization guidelines recommend that when a patient's CD4 count -- a measure of the strength of a person's immune system -- falls below 200, they should start antiretroviral therapy.

But that shouldn't be automatic with women who received single-dose nevirapine during labor, Essex said. "For many of them, it's almost certainly OK to wait for six months and then you can put them on" a nevirapine-based treatment.