LOS ANGELES, Feb. 9-- New studies show that the use of antiretroviral drugs by mother or baby for several months after delivery can significantly reduce the risk of transmitting the AIDS virus during breast-feeding.

One research, presented at the Conference on Retroviruses and Opportunistic Infections in Boston this week, found that the typical 15 percent infection rate of HIV from breast-feeding could be cut about in half by administering AIDS drugs for a longer period.

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

In another study led by the U.S. Centers for Disease Control and Prevention, HIV-infected mothers in Kenya received a triple-drug regimen for about six months. About 6 percent of these women's breast-fed infants got infected with the virus after a year.

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

"Breast-feeding is the final frontier of preventing mother-to-child transmission," Dr. Jeffrey Stringer, who directs the Center for Infectious Disease Research in Zambia, said in remarks published by the Los Angeles Times on Saturday.