Boston ? The use of antiretroviral drugs by mother or baby for several months after delivery can reduce the risk of transmitting the AIDS virus significantly during breast-feeding, researchers reported.

Public health officials have had great success blocking HIV transmission to newborns using the drugs AZT and nevirapine around the time of delivery, but have had few tools to prevent transmission through breast-feeding.

The research found that the typical 15 percent infection rate from breast-feeding could be cut roughly in half by administering AIDS drugs for a longer period.

One study based in Malawi found that 8 percent of infants who received an initial drug treatment around delivery plus 14 more weeks of AIDS medications were infected with HIV after nine months, compared to about 13 percent of the group receiving only the initial treatment.