Evaluating the impact of PMTCT of HIV in Malawi: an immunization clinic-based surveillance approach

Thesis (Dr.P.H.)--Boston UniversityBackground: Prevention of mother-to-child transmission of HIV (PMTCT) is an important component of HIV programs in generalized epidemics. Malawi has made significant progress in expanding access to PMTCT services, yet little information is available to assess the impact on transmission rates. Surveillance to assess transmission rates is particularly important given the recent adoption of the 'Option B+' strategy, offering all HIV-positive pregnant and breastfeeding women life-long antiretroviral therapy. This evaluation introduced a novel surveillance approach to assess rates of mother-to-child transmission and to gauge feasibility for implementation in Malawi. Methods: Estimates of the vertical transmission rate were derived by testing a population-based sample of infants presenting for their first immunization clinic visit in four districts. Fifty-three clinics were sampled randomly and all caregivers of infants < 3 months old attending the immunization clinic were invited to participate. Infant dried blood spot (DBS) samples were tested for HIV exposure with an antibody test to determine maternal seropositivity. Positive samples were tested for HIV antigen using DNA PCR to determine infant seropositivity and the vertical transmission rate. Caregivers were surveyed about maternal receipt of PMTCT services. Findings: Of the 5,068 DBS samples included in the analysis 764 were ELISA positive, indicating 15.1% (14.1-16.1 %) of mothers were HIV-infected and had passed HIV antibodies to their infant. Sixty-five of the 764 ELISA-positive samples tested positive with DNA PCR, indicating a vertical transmission rate of 8.5% (6.6-10.7%). Survey data indicated 64.8% ofHIV positive mothers and 46.9% ofHIV exposed infants received some form of antiretroviral prophylaxis. · Conclusions: The observed vertical transmission rate was substantially lower than earlier modeled analyses, suggesting that Malawi's PMTCT program has generated substantial benefits through averting perinatal HIV infection. However, challenges to implementation of PMTCT remain, particularly around low reported coverage of antiretroviral prophylaxis for both mothers and infants. The evaluation approach was successfully carried out by existing clinic staff and can likely be scaled up successfully to assess temporal changes in PMTCT effectiveness in Malawi as Option B+ is introduced