Evaluating the Impact of Prevention of Mother-to-Child Transmission of HIV in Malawi through Immunization Clinic-Based Surveillance

BACKGROUND Prevention of mother-to-child transmission of HIV (PMTCT) programs can greatly reduce the vertical transmission rate (VTR) of HIV, and Malawi is expanding PMTCT access by offering HIV-infected pregnant women life-long antiretroviral therapy (Option B+). There is currently no empirical data on the effectiveness of Malawian PMTCT programs. This study describes a surveillance approach to obtain population-based estimates of the VTR of infants <3 months of age in Malawi immediately after the adoption of Option B+. METHODS AND FINDINGS A sample of caregivers and infants <3 months from 53 randomly chosen immunization clinics in 4 districts were enrolled. Infant dried blood spot (DBS) samples were tested for HIV exposure with an antibody test to determine maternal seropositivity. Positive samples were further tested using DNA PCR to determine infant infection status and VTR. Caregivers were surveyed about maternal receipt of PMTCT services. Of the 5,068 DBS samples, 764 were ELISA positive indicating 15.1% (14.1-16.1%) of mothers were HIV-infected and passed antibodies to their infant. Sixty-five of the ELISA-positive samples tested positive by DNA PCR, indicating a vertical transmission rate of 8.5% (6.6-10.7%). Survey data indicates 64.8% of HIV-infected mothers and 46.9% of HIV-exposed infants received some form of antiretroviral prophylaxis. Results do not include the entire breastfeeding period which extends to almost 2 years in Malawi. CONCLUSIONS The observed VTR was lower than expected given earlier modeled estimates, suggesting that Malawi's PMTCT program has been successful at averting perinatal HIV transmission. Challenges to full implementation of PMTCT remain, particularly around low reported antiretroviral prophylaxis. This approach is a useful surveillance tool to assess changes in PMTCT effectiveness as Option B+ is scaled-up, and can be expanded to track programming effectiveness for young infants over time in Malawi and elsewhere.