Mathematical modelling of the influence of serosorting on the population-level HIV transmission impact of pre-exposure prophylaxis. (1st June 2021)

• Record Type: Journal Article
• Authors: Wang, Linwei; Moqueet, Nasheed; Simkin, Anna; Knight, Jesse; Ma, Huiting; Lachowsky, Nathan J.; Armstrong, Heather L.; Tan, Darrell H.S.; Burchell, Ann N.; Hart, Trevor A.; Moore, David M.; Adam, Barry D.; Macfadden, Derek R.; Baral, Stefan; Mishra, Sharmistha
• Is Part Of: AIDS. Volume 35:Number 7(2021)
• Publication Date: 2021-06-01
• Subjects: HIV -- MSM -- pre-exposure prophylaxis -- serosorting -- sexual mixing patterns; AIDS (Disease) -- Periodicals; Acquired Immunodeficiency Syndrome; AIDS (Disease); Periodicals; Periodicals; 616.9792005
• DOI: 10.1097/QAD.0000000000002826
• Languages: English
• ISSNs: 0269-9370

Abstract

Abstract : Objectives: HIV pre-exposure prophylaxis (PrEP) may change serosorting patterns. We examined the influence of serosorting on the population-level HIV transmission impact of PrEP, and how impact could change if PrEP users stopped serosorting. Design: We developed a compartmental HIV transmission model parameterized with bio-behavioural and HIV surveillance data among MSM in Canada. Methods: We separately fit the model with serosorting and without serosorting [counterfactual; sero-proportionate mixing (random partner-selection proportional to availability by HIV status)], and reproduced stable HIV epidemics with HIV-prevalence 10.3–24.8%, undiagnosed fraction 4.9–15.8% and treatment coverage 82.5–88.4%. We simulated PrEP-intervention reaching stable pre-specified coverage by year-one and compared absolute difference in relative HIV-incidence reduction 10 years post-intervention (PrEP-impact) between models with serosorting vs. sero-proportionate mixing; and counterfactual scenarios when PrEP users immediately stopped vs. continued serosorting. We examined sensitivity of results to PrEP-effectiveness (44–99%; reflecting varying dosing or adherence levels) and coverage (10–50%). Results: Models with serosorting predicted a larger PrEP-impact than models with sero-proportionate mixing under all PrEP-effectiveness and coverage assumptions [median (interquartile range): 8.1% (5.5–11.6%)]. PrEP users' stopping serosorting reduced PrEP-impact compared with when PrEP users continued serosorting: reductions in PrEP-impact were minimal [2.1% (1.4–3.4%)] under high PrEP-effectiveness (86–99%); however, could be considerable [10.9% (8.2–14.1%)] under low PrEP effectiveness (44%) and high coverage (30–50%). Conclusion: Models assuming sero-proportionate mixing may underestimate population-level HIV-incidence reductions due to PrEP. PrEP-mediated changes in serosorting could lead to programmatically important reductions in PrEP-impact under low PrEP-effectiveness. Our findings suggest the need to monitor sexual mixing patterns to inform PrEP implementation and evaluation. Abstract : Supplemental Digital Content is available in the text