Decline in rate of mother-to-child transmission of HIV-1 over time in Africa: Possible role of stage of the epidemic

Abstract

There is evidence worldwide of a temporal decline in mother-to-child transmission rates for HIV-1 infection. Although this is generally attributed to increased use of zidovudine in industrialized countries timing of the decline in such countries and observations in the developing world both raise the possibility of a general decline in the absence of antiretroviral therapy. Cost- effectiveness of interventions could vary dramatically over time and must be considered by policy makers particularly in the developing world. Recommended modifications in obstetric practice may have played a role in declining rates of vertical transmission. However there are two reasons linked to stage of the human immunodeficiency virus-acquired immunodeficiency syndrome (HIV-AIDS) epidemic why a dramatic fall in mother-to-child transmission rate is to be expected in the absence of specific interventions at least in Africa. Early in an epidemic most HIV-positive women are recently infected and many experience primary HIV infection during pregnancy. Delay in achieving viral “Set point” could result in high risk of transmission in uteri intrapartum and during breastfeeding. Cytotoxic CD8 cells remain high for up to 6 months after infection and high CD8 levels in pregnancy have been associated with mother-to- child transmission. Rates of transmission of 50% have been observed in such patients. It is striking that African reports of high mother-to-child transmission are from early in the epidemic in the study location (Table 1). (excerpt)