Reducing pediatric HIV infection: estimating mother to child transmission rates in a program setting in Zambia

BACKGROUND: Vertical transmission of HIV remains the main source of pediatric HIV infection in Africa with transmission rates as high as 25%-45% without intervention. Even though effective interventions to reduce vertical transmission of HIV are now available and remarkable progress has been made in scaling up prevention of mother-to-child transmission (PMTCT) services, the effectiveness of PMTCT interventions is unknown in Zambia. In this study, we estimate HIV vertical transmission rates at different age bands among perinatally exposed children.METHODS: The study analyzed program data of DNA polymerase chain reaction results and selected client information on dried blood spot samples from perinatally exposed children aged 0-12 months sent to the polymerase chain reaction laboratory from 5 provinces between September 2007 and January 2009.RESULTS: Samples of 8237 babies between 0 and 12 months were analyzed, with 84% of the mothers having ever breastfed their children. The observed transmission rate was 6.5% (5.1%, 7.8%) among infants aged 0-6 weeks when both mother and infant received interventions compared with 20.9% (12.3%, 29.5%) where no intervention was given to either mother or baby. Observed HIV transmission with single-dose nevirapine (sdNVP) was 8.5% (5.9%, 11.0%) among infants aged 0-6 weeks, whereas zidovudine with sdNVP (zidovudine + NVP) and highly active antiretroviral therapy were associated with observed transmission rates of 6.8% (4.5%, 9.1%) and 5.0% (3.0%, 7.0%), respectively; whereas these estimates were not significantly different from one another, they were all significantly lower than no intervention for which the estimated rate was 20.9%. Regardless of the intervention, the observed transmission rates were higher among infants aged 6-12 months.CONCLUSIONS: PMTCT interventions, including sdNVP, are working in program settings. However, postnatal transmission especially after 6 months through suboptimal feeding practises remains an important challenge to further reduce pediatric HIV