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Effects of Scaling Up Preexposure Prophylaxis on HIV Incidence in Men Who Have Sex with Men: An Application of Causal Inference Methodology

17 Pages Posted: 8 Jun 2022

See all articles by Ainesh Sewak

Ainesh Sewak

University of Zurich - Epidemiology, Biostatistics and Prevention Institute

Sara Lodi

Boston University - Boston University School of Public Health

Xiaojuan Li

Harvard Pilgrim Health Care

Di Shu

University of Pennsylvania - Department of Biostatistics, Epidemiology, and Informatics

Lan Wen

University of Waterloo - Department of Statistics and Actuarial Science

Kenneth H. Mayer

Fenway Community Health - The Fenway Institute

Douglas Krakower

Harvard Pilgrim Health Care

Jessica Young

Harvard Pilgrim Health Care

Julia Marcus

Harvard Pilgrim Health Care

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Abstract

Background: Uptake of preexposure prophylaxis (PrEP) has been limited and inequitable. Although interventions to increase PrEP uptake are being evaluated in clinical trials among men who have sex with men (MSM), those trials cannot evaluate effects on the rare outcome of HIV incidence. Estimates from observational studies of the causal effects of PrEP uptake interventions on HIV incidence can inform decisions about intervention scale-up.

Methods: We used electronic health record data from HIV-negative MSM accessing care at Fenway Health, a community health centre in Boston, Massachusetts, USA, from January 2012 through February 2018, with two years of follow-up. We considered stochastic interventions that increased the chance of initiating PrEP in several high-priority subgroups. We estimated the effects of these interventions on population-level HIV incidence using a novel inverse probability weighted estimator of the generalized g-formula, adjusting for baseline and time-varying confounders.

Findings: Of 11,055 MSM, 2875 (26%) initiated PrEP during follow-up. We estimated an intervention that increased the probability of initiating PrEP by 10% in MSM tested for rectal STIs resulted in an increase in PrEP initiation among all MSM from the observed 26% to 48% (95% CI 47% to 49%), and a relative reduction in two-year HIV risk among all MSM of 27% (95% CI 8% to 43%). Interventions of the same strength among Black or Latino MSM increased PrEP initiation among all MSM from 26% to 35% (95% CI 34% to 36%), with a relative reduction in HIV risk of 22% (95% CI 6% to 36%). The intervention among Black or Latino MSM was the most efficient, yielding the largest reduction in population-level HIV risk relative to the increase in the total proportion initiating PrEP.

Interpretation: Interventions that yield only modest increases in PrEP initiation in high-priority subgroups of MSM could meaningfully reduce HIV incidence in the overall population of MSM. Interventions tailored to Black and Latino MSM should be prioritized to maximize equity and impact. 

Funding: National Institute of Allergy and Infectious Diseases.

Declaration of Interest: KHM has received unrestricted research grants from Gilead Sciences and served on a Scientific Advisory Board for them. DSK has conducted research at Fenway Health funded by grants from Merck and has received personal fees for developing medical education content for DKBMed, Virology Education and UpToDate, Inc. JLM previously consulted for Kaiser Permanente Northern California on a research grant from Gilead Sciences unrelated to the submitted work. All other authors declare no conflicts of interests.

Ethical Approval: The institutional review boards at the Harvard Pilgrim Health Care Institute and Fenway Community Health determined this study to be exempt from review per 45 CFR Part 46 or 21 CFR Part 56, and that the information to be reviewed was fully de-identified per the HIPAA safe harbor standard, with no privacy review or approval of a HIPAA waiver required.

Keywords: Causal inference, HIV, inverse probability weighting, men who have sex with men (MSM), preexposure prophylaxis (PrEP), stochastic interventions

Suggested Citation

Sewak, Ainesh and Lodi, Sara and Li, Xiaojuan and Shu, Di and Wen, Lan and Mayer, Kenneth H. and Krakower, Douglas and Young, Jessica and Marcus, Julia, Effects of Scaling Up Preexposure Prophylaxis on HIV Incidence in Men Who Have Sex with Men: An Application of Causal Inference Methodology. Available at SSRN: https://ssrn.com/abstract=4124060 or http://dx.doi.org/10.2139/ssrn.4124060

Ainesh Sewak

University of Zurich - Epidemiology, Biostatistics and Prevention Institute ( email )

Sara Lodi

Boston University - Boston University School of Public Health ( email )

Boston, MA
United States

Xiaojuan Li

Harvard Pilgrim Health Care ( email )

Di Shu

University of Pennsylvania - Department of Biostatistics, Epidemiology, and Informatics ( email )

Lan Wen

University of Waterloo - Department of Statistics and Actuarial Science ( email )

Kenneth H. Mayer

Fenway Community Health - The Fenway Institute ( email )

Douglas Krakower

Harvard Pilgrim Health Care ( email )

Jessica Young

Harvard Pilgrim Health Care ( email )

Julia Marcus (Contact Author)

Harvard Pilgrim Health Care ( email )

93 Worcester Street
Wellesley, 02481
United States