Short course zidovudine cuts vertical transmission of HIV

A short course of the anti-HIV drug zidovudine can halve the rate of mother to child transmission in women who do not breastfeed and can reduce transmission among those who do by one third, according to the latest research.

The regimen could benefit thousands of babies in developing countries, where 90%of infant infections occur, and where previously there has been no strategy to reduce the risk of transmission. Every year 600000 infants are born with HIV. Without intervention 15–30%of babies are infected during labour and a further 15–30% through breastfeeding.

The short course of zidovudine treatment is a simplified version of that developed in 1994 by the Pediatric AIDS Clinical Trials Group (known as the 076 protocol), which was shown to reduce transmission rates by 68

Under protocol 076, women take zidovudine tablets five times daily between the 14th and 34th week of pregnancy followed by intravenous zidovudine during labour and delivery; their babies receive the drug orally for six weeks. This has become standard practice in the United States and Europe, reducing perinatal transmission rates to 6%or less.

The cost and complexity of this regimen, however, has made it unsuitable for use in developing countries. A battery of alternative treatment strategies has since been developed by the UNAIDS Working Groups on Mother to Infant Transmission, three strategies of which were reported in last week's Lancet.

In a study in Bangkok, oral zidovudine was used twice daily by mothers from 36 weeks of pregnancy until delivery, and babies received no drugs (Lancet 1999;353:773-80). A total of 397 women were randomly allocated to receive either zidovudine treatment or placebo, and all agreed not to breastfeed. This short course of antiretroviral treatment reduced transmission rates from 18.9%among women taking placebo to 9.4%in the treatment group.

When implemented nationally in Thailand this regimen could prevent about 2000 perinatal infections with HIV-1 annually, the researchers conclude. If implemented in other countries with higher HIV-1 burdens, the impact would be far greater.

In the two other studies, which were performed in Africa, women were allowed to breastfeed because there was no safe alternative and because women feared that if they did not breastfeed their HIV status would be revealed and they would be ostracised (Lancet 1999;353:781-5). The short course Thai regimen reduced rates of HIV transmission by 37%at three months even when women breast fed their infants, in a study carried out in Cite d‘Ivoire.

In the other African trial, with a similar treatment protocol, in which zidovudine was continued for one week after delivery, transmission rates fell by 38%at six months (Lancet 1999; 353:786-92).

Although the results are encouraging, Dr Lynne Mofenson of the US National Institutes of Health believes that there are still many barriers to implementing worldwide treatment strategies for pregnant women who are infected with HIV.

“Although short course zidovudine is cheaper than PACTG 076 regimen (about $50 vs $800), its cost is still prohibitive for many developing countries,” she writes in a commentary (Lancet 1999;353:766-7).

Antenatal care needs to be improved in many places (currently a third of women worldwide receive none), and HIV testing and counselling services need to be more widely available, she adds.

According to Dr Nathan Shaffer of the US Centers for Disease Control and Prevention who headed the study in Thailand, Unicef and UNAIDS are now coordinating an effort to implement pilot treatment projects based on the short course regimen in 10 countries on three continents.

Short course zidovudine could benefit babies in developing countries

Photo credit: IAN TEH/PANOS PICTURES