Impact of Early Antiretroviral Therapy Eligibility on HIV Acquisition: Household-Level Evidence from Rural South Africa

Antiretroviral therapy (ART) is highly effective in reducing HIV transmission from infected individuals to their non-infected partners. The landmark HPTN052 trial demonstrated a 96 percent reduction in linked HIV transmissions in couples who immediately initiated ART compared with deferred ART initiation. Early initiation of ART results in rapid and sustained viral suppression over time, whereas individuals who delay ART initiation are more likely to have a detectable viral load and are more likely to transmit the disease. Patients with higher CD4 white blood cell counts, indicating less severe disease, may be especially likely to face delays in starting treatment.

Beyond the individual relationship level, there may also be a relationship between ART uptake and HIV incidence within households. Individuals initiating ART may have social influence over HIV-uninfected household members. They may be more willing to disclose their status to their families and may discuss HIV prevention or counseling with family members, which could result in changes in HIV acquisition in households. This could result in spillover effects including changes in sexual behaviors among household members of ART patients, such as increases in condom use or reductions in number of partners.

In a new journal article published in the journal AIDS, Jacob Bor and coauthors use data from HIV patients in rural South Africa to estimate the causal effect of immediate versus delayed ART initiation on HIV incidence in household members. Household members of patients were eligible to participate in the study if they had at least two HIV tests and were HIV-uninfected when their family member began treatment.

Main findings:

• The probability of initiation of ART within six months was highest among patients who presented below the threshold of 200 CD4 cells/μl.
• Immediate initiation of ART reduced HIV incidence among patients’ uninfected household members by 47 percent.
• Although there was some variation in the reduction of HIV incidence with different model specifications, alternate specifications of the model indicate that the true magnitude of reduction is likely closer to 50 percent.

The study suggests that there are benefits to entire households when HIV-infected household members are immediately eligible for ART. The household-wide impact is driven by both biological reduction in transmission risk among sex partners of the person on ART, as well as potential changes in behavior among HIV-uninfected household members such as increased condom use, sexual awareness and risk protection. Taken together, the results support policies that eliminate ART eligibility thresholds and utilize interventions to rapidly increase ART coverage through expansions of HIV treatment programs.