Background
Despite universal test and treat for HIV, vertical transmission continues to occur. We evaluated the temporal effectiveness of vertical transmission prevention (VTP) over three maternal antiretroviral treatment (ART) policy periods (1. three-drug ART accessible to those with CD4 counts <200 cells/µl; 2. <350 cells/µl; 3. universal ART) in Western Cape, South Africa using routine provincial public sector individuated data.
Methods
We conducted a retrospective cohort study with child HIV acquisition as the primary outcome. Pregnancies between 2010 and 2020 were enumerated using the Provincial Health Data Centre Maternity Cascade which links electronic records of patients with administrative or laboratory evidence indicative of pregnancy. A child was deemed HIV exposed if their mother had electronic records indicative of HIV antenatally or ≤2 years from delivery. HIV and ART status were determined using indicators from laboratory, pharmacy and administrative information systems. Multivariable logistic regression was used to explore associations with vertical transmission.
Results
The proportion of mothers initiating ART prior to pregnancy increased from 20.9% in 2010 to 71.1% in 2020. Of the 842 641 pregnancies included, 17.1% were HIV exposed and 16.3% had a recorded child HIV outcome. Of children with maternal HIV exposure, 2.1% (95% CI 2.1 – 2.2) were diagnosed with HIV. The proportion of exposed children with unknown HIV status decreased (66.9% in 2010 to 12.8% in 2020) whilst those testing HIV negative increased (30.4% in 2010 to 85.5% in 2020). Overall, 22.9% of the 3966 children with HIV had apparent negative or unknown maternal exposure. Median time from birth to HIV diagnosis was 181 days (IQR 33 – 603). Children born in maternal ART policy period 3 were less likely to be diagnosed with HIV than children born in policy period 2 (aOR 0.66; 95% CI 0.60 – 0.72), mediated through expanded ART access. Young maternal age, no antenatal ART, previous TB diagnosis and no evidence of antenatal care attendance prior to delivery were associated with vertical transmission of HIV.
Conclusions
Our study demonstrates the positive impact of maternal ART policy change on VTP. The higher risk of vertical transmission amongst young women and those without antenatal care, highlights the need for targeted interventions for high-risk groups. The number of infections in children without established exposure emphasizes the importance of repeat antenatal and postnatal testing.
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