Aids is one of the principal causes of infant mortality in many developing countries. Viral transmission takes place during pregnancy (in utero), at the moment of childbirth or even during breastfeeding. If no treatment is given, the virus is transmitted to about 35% of children of infected mothers.
The use of a preventive treatment with zidovudine (AZT) has, since the 1990s, cut this risk to a third. However, access to these treatments remains scarcely possible for seropositive women living in developing countries, because of their duration, complexity and cost.
A clinical trial conducted in Thailand by a team of Thai, American and French researchers (1), as part of the international programme Perinatal HIV Prevention Trial (PHPT-2), showed that it is now possible to reduce the risk of mother-child HIV transmission to below the 2% threshold. This is possible using a combination of a short AZT treatment and a single dose of another antiretroviral, nevirapine (NVP).
In Thailand, the short treatment usually prescribed for prevention of mother-child HIV transmission is based on the administration of AZT in the course of the last three months of pregnancy and during labour and childbirth, and for one week in the newborn child. Bottle-feeding is also recommended, in order to avoid the child’s contamination by its mother’s milk. The researchers suggested adding to this treatment the administration of a single dose of NVP to both mother and child. The trial had the participation of 1 844 pregnant HIV-infected women, with a distribution over 37 hospitals over the whole country. Once their consent had been ensured, they were split at random into 3 groups. In the first group mothers and children received only the standard treatment using AZT. In the second group mothers received, in addition to the AZT treatment, a single dose of NVP at the moment of childbirth. For the third group, a single dose of NVP was added to the treatment of mothers and children.
A significantly lower transmission rate (3) was observed in groups taking the AZT-nevirapine combination, compared with the group receiving AZT (respectively 1.1 and 6.3%). This prompted the administration of nevirapine to all the women in the study. The trial was continued to determine if it was also necessary to give NVP to children, as an additive to milk. The final analysis showed a transmission rate of 2.0% in the group where both mothers and children had been treated with NVP and 2.8% in the group where only the mothers had taken it.