Modeling the potential impact of viral load monitoring on vertical transmission of HIV in Kenya.

Introduction: Viral load monitoring among pregnant and breastfeeding women (PBFW) can reduce vertical transmission by identifying PBFW with unsuppressed viral load and promoting re-suppression. However, the impact of varying degrees of adherence to viral load monitoring guidelines on the prevention of vertical transmission (PVT) is unknown.

Methods: We developed a microsimulation model of HIV progression and PVT care for PBFW living with recently acquired HIV in Kenya. We used this model to evaluate viral load monitoring in two key maternal populations: newly positive pregnant women who initiate ART during antenatal care and known positive women who are diagnosed and initiate ART prior to conception. For each population, we simulated three levels of adherence to Kenyan viral load monitoring guidelines during pregnancy and 18 months of breastfeeding: no testing; 50% adherence to indicated viral load tests (VL-50%); and 100% adherence (VL-100%). We evaluated viral load monitoring in each population by comparing live births, maternal deaths, and vertical transmission under VL-50% and VL-100% to no testing.

Results: Under no testing, infants acquired HIV at a rate of 619 vs. 505 per 10 000 live births in the newly positive vs. known positive populations, respectively. Viral load monitoring reduced vertical transmission by 1.6-2.7% in newly positive women vs. 9.1-14.3% in known positive women, and it reduced maternal deaths by 1.2-1.8% vs. 1.6-2.3%.

Conclusion: Maternal viral load monitoring in Kenya has considerably greater potential for achieving relative reductions in vertical transmission among known positive women than among newly positive women. In known positive women, even imperfect adherence to guidelines may achieve substantial relative reductions in vertical transmission.