To the Editor.
—The article by Dickover et al1 reporting differential risks of vertical transmission of HIV-1 infection perinatally1 begs questions in 3 distinct areas.The first concern is the antiviral therapeutic base for some of the conclusions. The dose-independent 1-hour serum half-life of zidovudine, following a peak concentration attained 0.5 to 1.5 hours after oral dosing, indicates that zidovudine should be given at least as frequently as the 4 times per day schedule recommended by the manufacturer and the Food and Drug Administration2 in order to maintain serum trough levels adequate to suppress proviral DNA transcription by even zidovudine-sensitive strains of HIV-1. Were the mothers-to-be in the study adequately dosed in these respects, ie, was the specified 500-mg total daily dose divided adequately and properly spaced in time? What objective verification was made, eg, by serum analysis, of patient compliance with the prescribed dosing, particularly during the last few