From conceptualising to modelling structural determinants and interventions in HIV transmission dynamics models: a scoping review and methodological framework for evidence-based analyses.

BACKGROUND: Including structural determinants (e.g. criminalisation, stigma, inequitable gender norms) in dynamic HIV transmission models is important to help quantify their population-level impacts and guide implementation of effective interventions that reduce the burden of HIV and inequalities thereof. However, evidence-based modelling of structural determinants is challenging partly due to a limited understanding of their causal pathways and few empirical estimates of their effects on HIV acquisition and transmission. METHODS: We conducted a scoping review of dynamic HIV transmission modelling studies that evaluated the impacts of structural determinants, published up to August 28, 2023, using Ovid Embase and Medline online databases. We appraised studies on how models represented exposure to structural determinants and causal pathways. Building on this, we developed a new methodological framework and recommendations to support the incorporation of structural determinants in transmission dynamics models and their analyses. We discuss the data and analyses that could strengthen the evidence used to inform these models. RESULTS: We identified 17 HIV modelling studies that represented structural determinants and/or interventions, including incarceration of people who inject drugs (number of studies [n] = 5), violence against women (n = 3), HIV stigma (n = 1), and housing instability (n = 1), among others (n = 7). Most studies (n = 10) modelled exposures dynamically. Almost half (8/17 studies) represented multiple exposure histories (e.g. current, recent, non-recent exposure). Structural determinants were often assumed to influence HIV indirectly by influencing mediators such as contact patterns, condom use, and antiretroviral therapy use. However, causal pathways' assumptions were sometimes simple, with few mediators explicitly represented in the model, and largely based on cross-sectional associations. Although most studies calibrated models using HIV epidemiological data, less than half (7/17) also fitted or cross-validated to data on the prevalence, frequency, or effects of exposure to structural determinants. CONCLUSIONS: Mathematical models can play a crucial role in elucidating the population-level impacts of structural determinants and interventions on HIV. We recommend the next generation of models reflect exposure to structural determinants dynamically and mechanistically, and reproduce the key causal pathways, based on longitudinal evidence of links between structural determinants, mediators, and HIV. This would improve the validity and usefulness of predictions of the impacts of structural determinants and interventions.

How Can Progress Toward Ending the Human Immunodeficiency Virus Epidemic in the United States Be Monitored?

The plan for Ending the HIV (human immunodeficiency virus) Epidemic (EHE) in the United States aims to reduce new infections by 75% by 2025 and by 90% by 2030. For EHE to be successful, it is important to accurately measure changes in numbers of new HIV infections after 5 and 10 years (to determine whether the EHE goals have been achieved) but also over shorter timescales (to monitor progress and intensify prevention efforts if required). In this viewpoint, we aim to demonstrate why the method used to monitor progress toward the EHE goals must be carefully considered. We briefly describe and discuss different methods to estimate numbers of new HIV infections based on longitudinal cohort studies, cross-sectional incidence surveys, and routine surveillance data. We particularly focus on identifying conditions under which unadjusted and adjusted estimates based on routine surveillance data can be used to estimate changes in new HIV infections.

Impact of pre-event testing and quarantine on reducing the risk of COVID-19 epidemic rebound: a modelling study.

BACKGROUND: With the evolving growth of the COVID-19 epidemic, travel restriction policies would need to be adjusted accordingly. Prohibition of mass event may be relaxed for social and economic benefits when virus transmission stops but could bear the risk of epidemic rebound. Against the background of the varied SARS-CoV-2 prevalence internationally, we modelled the potential impacts of pre-event interventions on epidemic risk of holding a mass event when COVID-19 is under control. METHODS: We developed a mathematical model of SARS-CoV-2 transmission in Guangdong Province, China, where local virus transmission ceased to occur. A large-scale international trade fair was assumed to be held, with influx of people from overseas and rest of China over a short period of time, who participated for 2-week. Scenarios of pre-event intervention (none, quarantine arrangement and polymerase chain reaction (PCR) testing for participants) were compared. The influence of contact pattern, SARS-CoV-2 prevalence outside the province and China, and testing coverage were examined in sensitivity analyses. RESULTS: In basecase scenario (no event), the epidemic has been under control since March 2020. The event would lead to the detection of 1% more confirmed cases by 31 July when community contact rate increases to pre-epidemic level. In event scenario without additional interventions, there would be 599 (93%) more new infections comparing with basecase scenario. To avert new infections, quarantining all participants before the event would be the most effective strategy, followed by quarantining all overseas participants and testing all other participants, and testing all participants before the event and on day 7. However, testing strategy is likely to be affected by the SARS-CoV-2 prevalence outside the event province. CONCLUSIONS: Pre-event interventions are effective for reducing the risk of epidemic rebound caused by an international large-scale event. Universal testing for participants is likely to be an effective and feasible intervention.

Modelling the impact of an HIV testing intervention on HIV transmission among men who have sex with men in China.

OBJECTIVES: An intervention developed through participatory crowdsourcing methods increased HIV self-testing among men who have sex with men [MSM; relative risk (RR) = 1.89]. We estimated the long-term impact of this intervention on HIV transmission among MSM in four cities (Guangzhou, Shenzhen, Jinan and Qingdao). METHODS: A mathematical model of HIV transmission, testing and treatment among MSM in China was parameterized using city-level demographic and sexual behaviour data and calibrated to HIV prevalence, diagnosis and antiretroviral therapy (ART) coverage data. The model was used to project the HIV infections averted over 20 years (2016-2036) from the intervention to increase self-testing, compared with current testing rates. RESULTS: Running the intervention once would avert < 2.2% infections over 20 years. Repeating the intervention (RR = 1.89) annually would avert 6.4-10.7% of new infections, while further increases in the self-testing rate (hypothetical RR = 3) would avert 11.7-20.7% of new infections. CONCLUSIONS: Repeated annual interventions would give a three- to seven-fold increase in long-term impact compared with a one-off intervention. Other interventions will be needed to more effectively reduce the HIV burden in this population.

Modelling the impact of a sex work crackdown on syphilis transmission among female sex workers and their clients in South China.

OBJECTIVE: To estimate the potential effects of an intense sex work crackdown on syphilis transmission in Guangdong Province, China. METHODS: We developed a deterministic compartmental model of syphilis transmission among female sex workers (FSW) and their male clients in Guangdong Province, China. We based model assumptions on census data and scientific literature, and we fitted the model to sentinel surveillance estimates of syphilis prevalence (positive results in both treponemal and non-treponemal tests) among FSW between 2009 and 2013. We estimated the impact of an intense sex work crackdown in 2014 by comparing the number of new syphilis infections between 2014 and 2020 in crackdown versus basecase (no crackdown) scenarios. In modelling scenarios, we examined main crackdown mechanisms of impact, including changed number of FSW engaging in sex work, reduction of weekly transactions, condom usage rate and syphilis diagnosis rate. RESULTS: In the basecase, predicted syphilis prevalence in FSW decreased from 2% in 2014 to 0.4% in 2020. In crackdown scenarios, syphilis incidence was predicted to transiently decrease and then to rebound relative to basecase levels a few years later. Shorter crackdowns led to higher, faster rebounds. CONCLUSIONS: Short-term intense crackdowns may exacerbate syphilis transmission among FSW and further marginalise an already vulnerable group. This study provides a quantitative, infection-related basis for changing sex work policies to reduce harms.

Under-Reporting of Known HIV-Positive Status Among People Living with HIV: A Systematic Review and Meta-analysis.

Monitoring progress towards the UNAIDS 'first 90' target requires accurate estimates of levels of diagnosis among people living with HIV (PLHIV), which is often estimated using self-report. We conducted a systematic review and meta-analysis quantifying under-reporting of known HIV-positive status using objective knowledge proxies. Databases were searched for studies providing self-reported and biological/clinical markers of prior knowledge of HIV-positive status among PLHIV. Random-effects models were used to derive pooled estimates of levels of under-reporting. Thirty-two estimates from 26 studies were included (41,465 PLHIV). The pooled proportion under-reporting known HIV-positive status was 20% (95% confidence interval 13-26%, I2 = 99%). In sub-group analysis, under-reporting was higher among men who have sex with men (32%, number of estimates [Ne] = 10) compared to the general population (9%, Ne = 10) and among Black (18%, Ne = 5) than non-Black (3%, Ne = 3) individuals. Supplementing self-reported data with biological/clinical proxies may improve the validity of the 'first 90' estimates.

Predicted Effectiveness of Daily and Nondaily Preexposure Prophylaxis for Men Who Have Sex With Men Based on Sex and Pill-taking Patterns From the Human Immuno Virus Prevention Trials Network 067/ADAPT Study.

BACKGROUND: The HIV Prevention Trials Network (HPTN) 067/Alternative Dosing to Augment PrEP Pill Taking (ADAPT) Study evaluated the feasibility of daily and nondaily human immunodeficiency virus (HIV) preexposure prophylaxis (PrEP) regimens among high-risk populations, including men who have sex with men (MSM) and transgender women, in Bangkok, Thailand and Harlem, New York. We used a mathematical model to predict the efficacy and effectiveness of different dosing regimens. METHODS: An individual-based mathematical model was used to simulate annual HIV incidence among MSM cohorts. PrEP efficacy for covered sex acts, as defined in the HPTN 067/ADAPT protocol, was estimated using subgroup efficacy estimates from the preexposure prophylaxis initiative (iPrEx) trial. Effectiveness was estimated by comparison of the HIV incidence with and without PrEP use. RESULTS: We estimated that PrEP was highly protective (85%-96% efficacy across regimens and sites) for fully covered acts. PrEP was more protective for partially covered acts in Bangkok (71%-88% efficacy) than in Harlem (62%-81% efficacy). Our model projects 80%, 62%, and 68% effectiveness of daily, time-driven, and event-driven PrEP for MSM in Harlem compared with 90%, 85%, and 79% for MSM in Bangkok. Halving the efficacy for partially covered acts decreases effectiveness by 8-9 percentage points in Harlem and by 5-9 percentage points in Bangkok across regimens. CONCLUSIONS: Our analysis suggests that PrEP was more effective among MSM in Thailand than in the United States as a result of more fully covered sex acts and more pills taken around partially covered acts. Overall, nondaily PrEP was less effective than daily PrEP, especially in the United States where the sex act coverage associated with daily use was substantially higher.

Crowdsourcing to expand HIV testing among men who have sex with men in China: A closed cohort stepped wedge cluster randomized controlled trial.

BACKGROUND: HIV testing rates are suboptimal among at-risk men. Crowdsourcing may be a useful tool for designing innovative, community-based HIV testing strategies to increase HIV testing. The purpose of this study was to use a stepped wedge cluster randomized controlled trial (RCT) to evaluate the effect of a crowdsourced HIV intervention on HIV testing uptake among men who have sex with men (MSM) in eight Chinese cities. METHODS AND FINDINGS: An HIV testing intervention was developed through a national image contest, a regional strategy designathon, and local message contests. The final intervention included a multimedia HIV testing campaign, an online HIV testing service, and local testing promotion campaigns tailored for MSM. This intervention was evaluated using a closed cohort stepped wedge cluster RCT in eight Chinese cities (Guangzhou, Shenzhen, Zhuhai, and Jiangmen in Guangdong province; Jinan, Qingdao, Yantai, and Jining in Shandong province) from August 2016 to August 2017. MSM were recruited through Blued, a social networking mobile application for MSM, from July 29 to August 21 of 2016. The primary outcome was self-reported HIV testing in the past 3 months. Secondary outcomes included HIV self-testing, facility-based HIV testing, condom use, and syphilis testing. Generalized linear mixed models (GLMMs) were used to analyze primary and secondary outcomes. We enrolled a total of 1,381 MSM. Most were ≤30 years old (82%), unmarried (86%), and had a college degree or higher (65%). The proportion of individuals receiving an HIV test during the intervention periods within a city was 8.9% (95% confidence interval [CI] 2.2-15.5) greater than during the control periods. In addition, the intention-to-treat analysis showed a higher probability of receiving an HIV test during the intervention periods as compared to the control periods (estimated risk ratio [RR] = 1.43, 95% CI 1.19-1.73). The intervention also increased HIV self-testing (RR = 1.89, 95% CI 1.50-2.38). There was no effect on facility-based HIV testing (RR = 1.00, 95% CI 0.79-1.26), condom use (RR = 1.00, 95% CI 0.86-1.17), or syphilis testing (RR = 0.92, 95% CI 0.70-1.21). A total of 48.6% (593/1,219) of participants reported that they received HIV self-testing. Among men who received two HIV tests, 32 individuals seroconverted during the 1-year study period. Study limitations include the use of self-reported HIV testing data among a subset of men and non-completion of the final survey by 23% of participants. Our study population was a young online group in urban China and the relevance of our findings to other populations will require further investigation. CONCLUSIONS: In this setting, crowdsourcing was effective for developing and strengthening community-based HIV testing services for MSM. Crowdsourced interventions may be an important tool for the scale-up of HIV testing services among MSM in low- and middle-income countries (LMIC). TRIAL REGISTRATION: ClinicalTrials.gov NCT02796963.

Protective immunity to Schistosoma haematobium infection is primarily an anti-fecundity response stimulated by the death of adult worms.

Protective immunity against human schistosome infection develops slowly, for reasons that are not yet fully understood. For many decades, researchers have attempted to infer properties of the immune response from epidemiological studies, with mathematical models frequently being used to bridge the gap between immunological theory and population-level data on schistosome infection and immune responses. Here, building upon earlier model findings, stochastic individual-based models were used to identify model structures consistent with observed field patterns of Schistosoma haematobium infection and antibody responses, including their distributions in cross-sectional surveys, and the observed treatment-induced antibody switch. We found that the observed patterns of infection and antibody were most consistent with models in which a long-lived protective antibody response is stimulated by the death of adult S. haematobium worms and reduces worm fecundity. These findings are discussed with regard to current understanding of human immune responses to schistosome infection.

Relationship between exposure to the Avahan intervention and levels of reported condom use among men who have sex with men in southern India.

BACKGROUND: The Avahan intervention promotes consistent (100%) condom use amongst men who have sex with men in southern India. We assessed how condom use varies with intervention exposure for men who have sex with men in Bangalore. METHODS: Self-reported condom use and intervention exposure data were derived from a cross-sectional survey. Consistent condom use and condom use at last sex act with all, main, and casual male sex partners were assessed. Binary and continuous variables reflecting intervention exposure (including contact(s) with intervention staff, receiving condoms and seeing condom demonstrations) were used. Multivariable logistic regression was employed to assess the relationship between condom use with each type of partner and each exposure variable independently, controlling for socio-demographic and behavioural factors associated with condom use or intervention exposure. RESULTS: Condom use with all partners was higher among those who had ever been contacted by, received condoms from, or seen a condom demonstration by intervention staff (adjusted odds ratio >2, p < 0.02 for all). Consistent condom use with all types of partner increased with the number of condom demonstrations seen in the last month (adjusted odds ratio = 2.1 per demonstration, p < 0.025), while condom use at last sex act with a casual (but not main) partner increased with the number of condoms received from the intervention (adjusted odds ratio = 1.4 per condom, p = 0.04). CONCLUSIONS: Direct contact with Avahan program staff is associated with increased reported condom use among men who have sex with men in Bangalore. Reported consistent condom use and condom use at last sex act are associated with contacts involving demonstrations of correct condom use, and with receiving condoms, respectively.

Integrated analysis of innate, Th1, Th2, Th17, and regulatory cytokines identifies changes in immune polarisation following treatment of human schistosomiasis.

BACKGROUND: Schistosomiasis elicits cross-regulatory immune responses, but it is unclear how antihelminthic treatment affects this balance. This study integrates data on 13 cytokines elicited by 3 schistosome to examine how praziquantel treatment alters immune polarization and whether post-treatment cytokine profiles influence reinfection status. METHODS: Venous blood from 72 Schistosoma haematobium-exposed participants was cultured with schistosome egg, adult worm, and cercaria antigens pre- and 6 weeks post-praziquantel treatment. Innate inflammatory (tumor necrosis factor α [TNF-α], interleukin(IL-)-6, IL-8), Th1 (interferon γ [IFN-γ], IL-2, IL-12p70), Th2 (IL-4, IL-5, IL-13), Th17 (IL-17A, IL-21, IL-23p19), and regulatory (IL-10) cytokines were quantified via enzyme-linked immunosorbent assay. Cytokine data was integrated using nonmetric multidimensional scaling and factor analysis. RESULTS: Egg-specific cytokine phenotypes became more proinflammatory post-treatment due to increased TNF-α, IL-6, IL-8, IFN-γ, IL-12p70, and IL-23 levels. Post-treatment cercariae-specific responses were also more proinflammatory reflecting elevated IL-8. In contrast, post-treatment adult worm-specific responses were less inflammatory, reflecting lower post-treatment IL-6. A combination of egg-induced IL-6, IL-12p70, IL-21, and IL-23 and adult worm-induced IL-5 and IL-21 post-treatment was associated with reduced reinfection risk 18 months later. CONCLUSIONS: Praziquantel treatment markedly alters polarization of schistosome-specific cytokine responses, and these changes, particularly in response to egg-stage parasites, may promote resistance to reinfection.

Comparison of Empirically Derived and Model-Based Estimates of Key Population HIV Incidence and the Distribution of New Infections by Population Group in Sub-Saharan Africa.

BACKGROUND: The distribution of new HIV infections among key populations, including female sex workers (FSWs), gay men and other men who have sex with men (MSM), and people who inject drugs (PWID) are essential information to guide an HIV response, but data are limited in sub-Saharan Africa (SSA). We analyzed empirically derived and mathematical model-based estimates of HIV incidence among key populations and compared with the Joint United Nations Programme on HIV/AIDS (UNAIDS) estimates. METHODS: We estimated HIV incidence among FSW and MSM in SSA by combining meta-analyses of empirical key population HIV incidence relative to the total population incidence with key population size estimates (KPSE) and HIV prevalence. Dynamic HIV transmission model estimates of HIV incidence and percentage of new infections among key populations were extracted from 94 country applications of 9 mathematical models. We compared these with UNAIDS-reported distribution of new infections, implied key population HIV incidence and incidence-to-prevalence ratios. RESULTS: Across SSA, empirical FSW HIV incidence was 8.6-fold (95% confidence interval: 5.7 to 12.9) higher than total population female 15-39 year incidence, and MSM HIV incidence was 41.8-fold (95% confidence interval: 21.9 to 79.6) male 15-29 year incidence. Combined with KPSE, these implied 12% of new HIV infections in 2021 were among FSW and MSM (5% and 7% respectively). In sensitivity analysis varying KPSE proportions within 95% uncertainty range, the proportion of new infections among FSW and MSM was between 9% and 19%. Insufficient data were available to estimate PWID incidence rate ratios. Across 94 models, median proportion of new infections among FSW, MSM, and PWID was 6.4% (interquartile range 3.2%-11.7%), both much lower than the 25% reported by UNAIDS. CONCLUSION: Empirically derived and model-based estimates of HIV incidence confirm dramatically higher HIV risk among key populations in SSA. Estimated proportions of new infections among key populations in 2021 were sensitive to population size assumptions and were substantially lower than estimates reported by UNAIDS.

Measuring HIV Acquisitions Among Partners of Key Populations: Estimates From HIV Transmission Dynamic Models.

BACKGROUND: Key populations (KPs), including female sex workers (FSWs), gay men and other men who have sex with men (MSM), people who inject drugs (PWID), and transgender women (TGW) experience disproportionate risks of HIV acquisition. The UNAIDS Global AIDS 2022 Update reported that one-quarter of all new HIV infections occurred among their non-KP sexual partners. However, this fraction relied on heuristics regarding the ratio of new infections that KPs transmitted to their non-KP partners to the new infections acquired among KPs (herein referred to as "infection ratios"). We recalculated these ratios using dynamic transmission models. SETTING: One hundred seventy-eight settings (106 countries). METHODS: Infection ratios for FSW, MSM, PWID, TGW, and clients of FSW were estimated from 12 models for 2020. RESULTS: Median model estimates of infection ratios were 0.7 (interquartile range: 0.5-1.0; n = 172 estimates) and 1.2 (0.8-1.8; n = 127) for acquisitions from FSW clients and transmissions from FSW to all their non-KP partners, respectively, which were comparable with the previous UNAIDS assumptions (0.2-1.5 across regions). Model estimates for female partners of MSM were 0.5 (0.2-0.8; n = 20) and 0.3 (0.2-0.4; n = 10) for partners of PWID across settings in Eastern and Southern Africa, lower than the corresponding UNAIDS assumptions (0.9 and 0.8, respectively). The few available model estimates for TGW were higher [5.1 (1.2-7.0; n = 8)] than the UNAIDS assumptions (0.1-0.3). Model estimates for non-FSW partners of FSW clients in Western and Central Africa were high (1.7; 1.0-2.3; n = 29). CONCLUSIONS: Ratios of new infections among non-KP partners relative to KP were high, confirming the importance of better addressing prevention and treatment needs among KP as central to reducing overall HIV incidence.

Economic evaluation of improving HIV self-testing among MSM in China using a crowdsourced intervention: a cost-effectiveness analysis.

OBJECTIVES: Crowdsourcing, which taps into the wisdom of crowds, has been successful in generating strategies to enhance HIV self-testing (HIVST) uptake. We determined the cost-effectiveness of a crowdsourced intervention (one-off or annual) compared with a control scenario (no crowdsourcing) among MSM living in China. DESIGN: Economic evaluation. METHODS: We used data from our cluster randomized controlled trial of MSM (NCT02796963). We used a micro-costing approach to measure direct health costs ($USD2017) from a health provider perspective. Using outputs from a dynamic transmission model over a 20-year time horizon, we estimated the incremental cost-effectiveness ratios using cost per disability-adjusted life years (DALYs) averted with 3% discounting. An intervention was considered highly cost-effective if it was less than one gross domestic product (GDP, $8823) per DALY averted. RESULTS: Across all cities, the crowdsourced intervention was highly cost-effective compared with the control scenario (incremental cost-effectiveness ratios ranged from $2263 to 6152 per DALY averted for annual crowdsourcing; $171 to 204 per DALY averted for one-off crowdsourcing). The one-off intervention was cost-saving in Guangzhou and Qingdao. Sensitivity analyses confirmed the robustness of the findings; specifically, changes in discounting, costs of the crowdsourced intervention, costs of HIV testing and cost of antiretroviral therapy did not alter our conclusions. CONCLUSION: Scaling up a one-off or annual crowdsourced HIV prevention intervention in four cities in China was very likely to be cost-effective. Further research is warranted to evaluate the feasibility of scaling up crowdsourced HIV prevention interventions in other settings and populations.

Trends in HIV testing, the treatment cascade, and HIV incidence among men who have sex with men in Africa: a systematic review and meta-analysis.

BACKGROUND: Gay, bisexual, and other men who have sex with men (MSM) are disproportionately affected by HIV. In Africa, MSM face structural barriers to HIV prevention and treatment that increase their vulnerability to HIV acquisition and transmission, and undermine the HIV response. In this systematic review, we aimed to explore progress towards increases in HIV testing, improving engagement in the HIV treatment cascade, and HIV incidence reductions among MSM in Africa. METHODS: We searched Embase, MEDLINE, Global Health, Scopus, and Web of Science for cross-sectional and longitudinal studies reporting HIV testing, knowledge of status, care, antiretroviral therapy (ART) use, viral suppression, and HIV incidence among MSM in Africa published between Jan 1, 1980, and March 3, 2023. We pooled surveys using Bayesian generalised linear mixed-effects models, used meta-regression to assess time trends, and compared HIV incidence estimates among MSM with those of all men. FINDINGS: Of 9278 articles identified, we included 152 unique studies published in 2005-23. In 2020, we estimate that 73% (95% credible interval [CrI] 62-87) of MSM had ever tested for HIV. HIV testing in the past 12 months increased over time in central, western, eastern, and southern Africa (odds ratio per year [ORyear] 1·23, 95% CrI 1·01-1·51, n=46) and in 2020 an estimated 82% (70-91) had tested in the past 12 months, but only 51% (30-72) of MSM living with HIV knew their HIV status. Current ART use increased over time in central and western (ORyear 1·41, 1·08-1·93, n=9) and eastern and southern Africa (ORyear 1·37, 1·04-1·84, n=17). We estimated that, in 2020, 73% (47-88) of all MSM living with HIV in Africa were currently on ART. Nevertheless, we did not find strong evidence to suggest that viral suppression increased, with only 69% (38-89) of MSM living with HIV estimated to be virally suppressed in 2020. We found insufficient evidence of a decrease in HIV incidence over time (incidence ratio per year 0·96, 95% CrI 0·63-1·50, n=39), and HIV incidence remained high in 2020 (6·9 per 100 person-years, 95% CrI 3·1-27·6) and substantially higher (27-199 times higher) than among all men. INTERPRETATION: HIV incidence remains high, and might not be decreasing among MSM in Africa over time, despite some increases in HIV testing and ART use. Achieving the UNAIDS 95-95-95 targets for diagnosis, treatment, and viral suppression equitably for all requires renewed focus on this key population. Combination interventions for MSM are urgently required to reduce disparities in HIV incidence and tackle the social, structural, and behavioural factors that make MSM vulnerable to HIV acquisition. FUNDING: US National Institutes of Health, UK Medical Research Council, Canadian Institutes of Health Research, and Fonds de Recherche du Québec-Santé. TRANSLATION: For the French translation of the abstract see Supplementary Materials section.

Estimating the impact of HIV PrEP regimens containing long-acting injectable cabotegravir or daily oral tenofovir disoproxil fumarate/emtricitabine among men who have sex with men in the United States: a mathematical modelling study for HPTN 083.

Background: The HPTN 083 trial demonstrated superiority of HIV pre-exposure prophylaxis (PrEP) containing long-acting injectable cabotegravir (CAB) to daily oral tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) among men who have sex with men (MSM). We compared the potential population-level impact of TDF/FTC and CAB among MSM in Atlanta, Georgia. Methods: An MSM HIV transmission model was calibrated to Atlanta-specific data on HIV prevalence and PrEP usage (percentage of uninfected MSM on PrEP), assuming only PrEP-indicated MSM used PrEP. CAB effectiveness (efficacy × adherence) of 91% was estimated using data from HPTN 083 and previous TDF/FTC trials. We estimated HIV infections averted over 5/10 years if TDF/FTC use were maintained, or if all TDF/FTC users switched to CAB in January 2022 (vs. no PrEP or continued TDF/FTC use). CAB scenarios with 10%/20% more users were also considered. Progress towards Ending the HIV Epidemic (EHE) goals (75%/90% fewer HIV infections in 2025/2030 vs. 2017) was estimated. Findings: We predicted TDF/FTC at current usage (∼28%) would avert 36.3% of new HIV infections (95% credible interval 25.6-48.7%) among all Atlanta MSM over 2022-2026 vs. no PrEP. Switching to CAB with similar usage may prevent 44.6% (33.2-56.6%) infections vs. no PrEP and 11.9% (5.2-20.2%) infections vs. continued TDF/FTC. Increasing CAB usage 20% could increase the incremental impact over TDF/FTC to 30.0% over 2022-2026, getting ∼60% towards reaching EHE goals (47%/54% fewer infections in 2025/2030). Reaching the 2030 EHE goal would require 93% CAB usage. Interpretation: If CAB effectiveness were like HPTN 083, CAB could prevent more infections than TDF/FTC at similar usage. Increased CAB usage could contribute substantially towards reaching EHE goals, but the usage required to meet EHE goals is unrealistic. Funding: NIH, MRC.

Efficacy estimates of oral pre-exposure prophylaxis for HIV prevention in cisgender women with partial adherence.

Pre-exposure prophylaxis (PrEP) with tenofovir (TFV) disoproxil fumarate and emtricitabine administered orally daily is effective in preventing human immunodeficiency virus (HIV) acquisition in both men and women with sufficient adherence; however, the adherence-efficacy relationship in cisgender women has not been well established. We calculated the adherence-efficacy curve for cisgender women by using HIV incidence and plasma TFV concentration data from three trials (FEM-PrEP, VOICE and Partners PrEP). We imputed TFV diphosphate (TFV-DP) concentrations, a measure of long-term adherence, from TFV quantification by using data from the HIV Prevention Trials Network 082 study, which measured both TFV-DP and TFV concentrations. Two, four and seven pills per week reduced HIV incidence by 59.3% (95% credible interval (CrI) 29.9-95.8%), 83.8% (95% CI 51.7-99.8%) and 95.9% (95% CI 72.6-100%), respectively. Our adherence-efficacy curve can be validated and updated by HIV prevention studies that directly measure TFV-DP concentrations. The curve suggests that high adherence confers high protection in cisgender women. However, the lower efficacy with partial adherence highlights the need for new PrEP products and interventions to increase adherence.

Population-level impact of expanding PrEP coverage by offering long-acting injectable PrEP to MSM in three high-resource settings: a model comparison analysis.

INTRODUCTION: Long-acting injectable cabotegravir (CAB-LA) demonstrated superiority to daily tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) for HIV pre-exposure prophylaxis (PrEP) in the HPTN 083/084 trials. We compared the potential impact of expanding PrEP coverage by offering CAB-LA to men who have sex with men (MSM) in Atlanta (US), Montreal (Canada) and the Netherlands, settings with different HIV epidemics. METHODS: Three risk-stratified HIV transmission models were independently parameterized and calibrated to local data. In Atlanta, Montreal and the Netherlands, the models, respectively, estimated mean TDF/FTC coverage starting at 29%, 7% and 4% in 2022, and projected HIV incidence per 100 person-years (PY), respectively, decreasing from 2.06 to 1.62, 0.08 to 0.03 and 0.07 to 0.001 by 2042. Expansion of PrEP coverage was simulated by recruiting new CAB-LA users and by switching different proportions of TDF/FTC users to CAB-LA. Population effectiveness and efficiency of PrEP expansions were evaluated over 20 years in comparison to baseline scenarios with TDF/FTC only. RESULTS: Increasing PrEP coverage by 11 percentage points (pp) from 29% to 40% by 2032 was expected to avert a median 36% of new HIV acquisitions in Atlanta. Substantially larger increases (by 33 or 26 pp) in PrEP coverage (to 40% or 30%) were needed to achieve comparable reductions in Montreal and the Netherlands, respectively. A median 17 additional PYs on PrEP were needed to prevent one acquisition in Atlanta with 40% PrEP coverage, compared to 1000+ in Montreal and 4000+ in the Netherlands. Reaching 50% PrEP coverage by 2032 by recruiting CAB-LA users among PrEP-eligible MSM could avert >45% of new HIV acquisitions in all settings. Achieving targeted coverage 5 years earlier increased the impact by 5-10 pp. In the Atlanta model, PrEP expansions achieving 40% and 50% coverage reduced differences in PrEP access between PrEP-indicated White and Black MSM from 23 to 9 pp and 4 pp, respectively. CONCLUSIONS: Achieving high PrEP coverage by offering CAB-LA can impact the HIV epidemic substantially if rolled out without delays. These PrEP expansions may be efficient in settings with high HIV incidence (like Atlanta) but not in settings with low HIV incidence (like Montreal and the Netherlands).

HTPN 078: an enhanced case management study to achieve viral suppression among viremic HIV-positive men who have sex with men in the United States.

OBJECTIVES: After identifying and recruiting men who have sex with men living with HIV and virally unsuppressed, this study attempted to enhance treatment and care via case management to increase the proportion who achieved viral suppression. DESIGN: Participants were randomized into one of two study arms: standard of care (SOC) or enhanced case management (CM) intervention. Participants were followed for 12 months with quarterly study assessments, with blood collected for CD4+ cell count testing, HIV viral load testing (primary prespecified outcome), and plasma storage. METHODS: Participants identified via respondent-driven sampling and direct recruitment and were invited to participate in the randomized controlled trial. The CM intervention provided a wide range of support services including, health education, clinical care coordination, medication adherence support, and social service assistance. The month-12 assessment included questions about healthcare utilization, stigma, substance use, and mental health. RESULTS: Among the 144 participants virally unsuppressed at baseline, most had had a previous positive HIV test result; were Black, non-Hispanic, gay and bisexual men, aged 22-50. Among the 128 participants at the last study visit, 68 were virally suppressed, with no statistically significant difference between the CM and SOC arms (viral suppression 42% and 53%, respectively; adjusted odds ratio = 0.62 [P = 0.15; 95% confidence interval: 0.32, 1.2]). CONCLUSIONS: Reaching targets of at least 90% sustained viral suppression among all people with HIV will likely require more than an individual-level CM approach that addresses barriers to optimal care and treatment at multiple levels.

Explaining observed infection and antibody age-profiles in populations with urogenital schistosomiasis.

Urogenital schistosomiasis is a tropical disease infecting more than 100 million people in sub-Saharan Africa. Individuals in endemic areas endure repeated infections with long-lived schistosome worms, and also encounter larval and egg stages of the life cycle. Protective immunity against infection develops slowly with age. Distinctive age-related patterns of infection and specific antibody responses are seen in endemic areas, including an infection 'peak shift' and a switch in the antibody types produced. Deterministic models describing changing levels of infection and antibody with age in homogeneously exposed populations were developed to identify the key mechanisms underlying the antibody switch, and to test two theories for the slow development of protective immunity: that (i) exposure to dying (long-lived) worms, or (ii) experience of a threshold level of antigen, is necessary to stimulate protective antibody. Different model structures were explored, including alternative stages of the life cycle as the main antigenic source and the principal target of protective antibody, different worm survival distributions, antigen thresholds and immune cross-regulation. Models were identified which could reproduce patterns of infection and antibody consistent with field data. Models with dying worms as the main source of protective antigen could reproduce all of these patterns, but so could some models with other continually-encountered life stages acting as the principal antigen source. An antigen threshold enhanced the ability of the model to replicate these patterns, but was not essential for it to do so. Models including either non-exponential worm survival or cross-regulation were more likely to be able to reproduce field patterns, but neither of these was absolutely required. The combination of life cycle stage stimulating, and targeted by, antibody was found to be critical in determining whether models could successfully reproduce patterns in the data, and a number of combinations were excluded as being inconsistent with field data.