Feasibility of using infant testing during immunization to estimate HIV mother-to-child-transmission rates in Zambia

BACKGROUND: This study piloted the feasibility of infant testing in immunization services as a strategy for estimating MTCT rates among the population of HIV exposed infants at national and subnational levels in Zambia. METHODS: The study recruited a cross-sectional nationally representative sample of 8042 caregiver-baby pairs in 38 high volume immunization sites in 7 towns across 3 provinces of Zambia. All mothers who brought their children below the age of one year for immunization at the study facilities were invited to participate in the study. All consenting mothers were interviewed and blood drawn from their babies for; rapid HIV antibody test to determine exposure and DNA PCR test for samples of all HIV-exposed babies to determine HIV infection. RESULTS: Of 8042 recruited caregiver–baby pairs, 1409 (17.5%) babies were HIV-exposed. Approximately 90.2% of all mothers of HIV exposed infants reported that they attended ANC visits more than two times and facility based deliveries stood at 91.6%. Exclusive breastfeeding among HIV exposed infants reduced with increase in age of infant; it was highest at 6 weeks (82.2%) followed by 10 weeks (74.0%) and 14 weeks (58.2%). MTCT rates were relatively lower than what was reported before in subnational studies and stood at 4.7% among Penta 1 seekers, 2.8% among Penta 2 seekers, 2.1% among Penta 3 seekers and 5.0% among Measles vaccination seekers. The overall MTCT rate stood at 3.8%. About 48.1% of HIV positive babies were male compared to 51.9% females. Babies of mothers below the age of 25 years accounted for almost half (51.9%) of all HIV infected babies in the study. Reported exclusive breastfeeding among HIV positive babies was 77.8% for Penta 1 seekers, 75.0% for Penta 2 seekers and 100% for Penta 3 seekers. CONCLUSIONS: The study succeeded in estimating the MTCT rates using infant testing in immunization services, thereby demonstrating that it is feasible to use routine infant testing in immunization services as a strategy for estimating MTCT rates among the population of HIV-exposed infants in countries with high HIV burden and immunization coverage.