Adaptive HIV pre-exposure prophylaxis adherence interventions for young women in Johannesburg, South Africa: a sequential multiple-assignment randomised trial

Background Adherence to daily oral pre-exposure prophylaxis (PrEP) is low among African young women, and layered support strategies are needed to improve PrEP adherence in this population. We aimed to evaluate potentially scalable adherence-support strategies for young women aged 18-25 years who initiated PrEP in Johannesburg, South Africa. Methods We conducted a sequential multiple-assignment randomised trial at Ward 21 of the Wits Reproductive Health and HIV Institute clinical research site, affiliated with University of the Witwatersrand, Johannesburg, South Africa. Participants were eligible if they were assigned female sex at birth, aged 18-25 years, not living with HIV, sexually active, newly initiating PrEP, had regular access to a mobile telephone, and could read. Using sequentially numbered, sealed, opaque envelopes containing group allocation, a staff member assigned enrolled participants (1:1) to receive one of two adherence-support interventions: once per week two-way SMS communication or participation in a WhatsApp peer-support group. Participants assigned to WhatsApp were put into groups with approximately 25 participants, during which they were prompted by staff facilitators to discuss any challenges with PrEP use or other events happening in their lives. The allocation sequence was generated by the data manager using random numbers with variable block sizes between 10 and 14. Only trial investigators were masked to participant intervention assignments; participants, people giving interventions, people assessing outcomes, and people analysing data were not masked to group assignment. All enrolled participants were offered PrEP (ie, co-formulated, once per day oral emtricitabine 200 mg and tenofovir disoproxil fumarate 300 mg). The primary outcome was high PrEP adherence at month 9, defined as concentration of tenofovir diphosphate on dried blood sample of 700 fmol per punch or more. At month 3, participants with low PrEP adherence were randomly assigned to a secondary, intensified intervention of issue-focused counselling once per month or drug-level feedback counselling based on PrEP drug concentrations at months 3 and 6. The protocol was registered at ClinicalTrials.gov (NCT04038060) and the trial is complete. Findings Participants were enrolled and followed up between May 16, 2019, and Jan 25, 2022. From May 16, 2019, to Jan 29, 2021, 401 participants were screened and 360 were enrolled and initiated PrEP. 180 (50%) were randomly assigned to two-way SMS and 180 (50%) were randomly assigned to WhatsApp support groups. At month 9, 34 (20%) of 174 participants in the two-way SMS arm had tenofovir diphosphate 700 fmol per punch or more, compared with 32 (18%) of 174 in the WhatsApp arm (relative risk 1<middle dot>06, 95% CI 0<middle dot>69-1<middle dot>64; p=0<middle dot>78). At month 9, four (5%) of 76 participants in the drug-level feedback arm had tenofovir diphosphate 700 fmol per punch or more, compared with three (4%) of 76 participants in the monthly counselling arm (1<middle dot>33, 0<middle dot>31-5<middle dot>76; p=0<middle dot>70). 22 serious adverse events were reported during the trial, but were all deemed unrelated to the trial. Interpretation PrEP adherence did not differ across interventions among young women in Johannesburg, South Africa. Future research is needed on whether and how to scale-up PrEP support for young women in resource-constrained settings. Copyright (c) 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.