In 1994, the AIDS Clinical Trials Group (ACTG) Protocol 076 Study Group announced that intensive zidovudine therapy reduced transmission of human immunodeficiency virus (HIV) from mother to child by nearly 70%.⁷ The regimen involved oral zidovudine five times daily for two to six months before delivery, intravenous zidovudine during labour, and zidovudine syrup administered six-hourly to newborn infants for six weeks. Mothers did not breast-feed their babies.

The ACTG 076 regimen is now a standard treatment for HIV-seropositive pregnant women in many developed countries. However, it is expensive -- drug costs alone are at least $US800 per course.⁸ Hence, few developing countries can afford it as a general public health intervention, although Glaxo Wellcome, the manufacturer of zidovudine, has announced plans to lower the price specifically for treatment of pregnant women in developing countries.⁹

Until recently, little was known about the effectiveness of less-intensive zidovudine regimens in reducing perinatal transmission.¹⁰ Some of the disputed trials aim(ed) to test precisely this. Others test(ed) the impact of alternative interventions, such as vitamin A and HIV immuneglobulin.

A study in Thailand, sponsored by the Centers for Disease Control, used a placebo-controlled design to assess a regimen involving zidovudine beginning three to four weeks before delivery, an oral dose of the drug during delivery, and no infant dose. Interim results showed that 9.2% of infants whose mothers received this intervention were infected, compared with 19% of infants whose mothers were randomised to receive placebo. Investigators thus attributed a 51% reduction in HIV vertical transmission rates to a regimen that costs about $US50 at current prices.^11,12