HIV incidence low in women with consistently high PrEP adherence

The incidence of HIV infection is very low among women who maintain consistently high levels of adherence to pre-exposure prophylaxis (PrEP) with emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF), according to findings published in JAMA.

Although previous research indicates that HIV PrEP with FTC/TDF is highly effective in cisgender men who have sex with men, there is a lack of evidence on the effectiveness of FTC/TDF and its relationship with adherence among cisgender women.

To characterize the effectiveness of PrEP with FTC/TDF among women, researchers conducted a study using pooled data from 7 demonstration projects and 4 open-label studies conducted across sub-Saharan Africa, India, and the United States. Patients included in the analysis were cisgender women (N=6296) who initiated PrEP with FTC/DTF between 2012 and 2020. The primary outcome was incident HIV infection through 96 weeks, which was evaluated on the basis of objective and subjective measures of treatment adherence. Objective adherence measures included TDF levels in dried blood spots and tenofovir levels in plasma; subjective adherence measures included patient self-report, electronic pill cap monitoring, and adherence scales.

Among patients included in the final analysis (N=6296), the mean (SD) age at PrEP initiation was 25 (7) years, 52% were married, 54% were nulliparous, and 21% reported engagement in transactional sex work. Patients predominantly resided in Kenya (46%), South Africa (28%), and India (21%).

A total of 32 incident HIV diagnoses were observed across the overall population (incidence rate [IR], 0.72 per 100 person-years; 95% CI, 0.51-1.01).

Stratified by patient characteristics, the incidence of HIV infection per 100 person-years was higher among younger (<25 years) vs older (≥25 years) patients (IR, 1.33 vs 0.24), married vs single patients (IR, 1.15 vs 0.66), and nulliparous patients vs those with children (IR, 1.68 vs 0.71).

Data on PrEP adherence were available for 2955 patients. The researchers noted that overall rates of self-reported subjective adherence were substantially higher (range, 67%-82%) than those of objective adherence (range, 20%-33%).

Further analysis was performed after patients were stratified into subgroups on the basis of adherence trajectory. Four subgroups were evaluated, including patients who consistently adhered to 7 PrEP doses weekly, those who adhered to 4 to 6 weekly doses, those who adhered to less than 2 weekly doses, and those with dynamic adherence that was initially high and declined over time.

Compared with patients aged 25 years and older, those younger than 25 were less likely to exhibit consistently high adherence to daily PrEP (odds ratio [OR], 0.42; 95% CI, 0.25-0.71), consistently high adherence to 4 to 6 weekly doses (OR, 0.82; 95% CI, 0.53-1.27), or dynamic adherence (OR, 0.51; 95% CI, 0.37-0.69). In addition, women who were nulliparous were less likely exhibit dynamic adherence compared with women with children (OR, 0.57; 95% CI, 0.34-0.97).

There were no HIV diagnoses reported among patients who maintained consistently high adherence to daily PrEP. However, the incidence of HIV infection among patients with consistently low, dynamic, or consistently high (4-6 doses weekly) PrEP adherence was 1.27, 0.49, and 0.13 per 100-person years, respectively.

Limitations of this analysis include the lack of data on subjective and objective measures of PrEP adherence from some patients, and the use of pooled data from heterogeneous studies.

“Even with the relatively low number of incident HIV diagnoses, a clear relationship was observed between evidence (both objective and subjective) of higher adherence with lower risk of HIV infection,” the researchers noted.

Disclosures: This research was supported by Gilead Sciences, and multiple study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.

References:

Marrazzo J, Becker M, Leech AA, et al. HIV Preexposure prophylaxis with emtricitabine and tenofovir disoproxil fumarate among cisgender women. JAMA. Published online March 1, 2024. doi:10.1001/jama.2024.0464