AIDS researchers in Uganda and the United States have found a way to reduce mother-to-child transmission of the AIDS virus far more cheaply and easily than previously possible.

The strategy cuts transmission in half by using about $3 worth of the long-acting antiviral drug nevirapine. Although less effective than the method used in the United States, which requires about $800 in drugs and months of treatment, this one is probably within reach of even the poorest countries.

Preliminary results of an experiment comparing nevirapine to an extremely short course of the antiviral drug AZT in 600 pregnant women were announced yesterday in Kampala, Uganda and at the National Institutes of Health, the federal agency that financed the study.