Can the combination of TasP and PrEP eliminate HIV among MSM in British Columbia, Canada?

A modeling study of pre-exposure prophylaxis to eliminate HIV in Taiwan by 2030

BACKGROUND

The necessity of pre-exposure prophylaxis (PrEP) for ending the global AIDS epidemic by 2030 remains controversial. In Taiwan, the HIV epidemic predominantly affects young, sexually active men who have sex with men (MSM). This study aimed to model the impact and cost-effectiveness of a high-coverage oral emtricitabine/tenofovir PrEP program in Taiwan from an HIV elimination perspective.

METHODS

We applied stochastic and risk/age-structured deterministic modeling to assess the impact of PrEP scale-up on the basic reproduction number (R0) and the trajectory of the HIV epidemic in Taiwan, respectively. Both models were parameterized using the national HIV registry and cascade data. Cost-effectiveness was evaluated from a societal perspective.

RESULTS

Here we show that an intensive HIV test-and-treat strategy targeting HIV-positive individuals alone would substantially decrease HIV transmission but is not sufficient to eliminate the HIV epidemic among MSM at the estimated mixing level. In contrast, a PrEP program covering 50% of young, sexually active, high-risk, HIV-negative MSM would suppress HIV's R0 below 1, facilitating its elimination. It would also reduce HIV incidence to levels below the World Health Organization's HIV elimination threshold (1/1000 person-years) by 2030 and is highly cost-saving, yielding a benefit-cost ratio of 7.16. The program's effectiveness and cost-effectiveness remain robust even under conditions of risk compensation (i.e., no condom use among PrEP users), imperfect adherence (75%), or low-level emtricitabine/tenofovir resistance (1%).

CONCLUSION

Our findings strongly support scaling up PrEP for young, sexually active, high-risk, HIV-negative MSM as a critical strategy to end the HIV epidemic in Taiwan and globally.

Dynamics of Mpox in an HIV endemic community: A mathematical modelling approach

During the 2022 monkeypox (Mpox) outbreak in non-endemic countries, sexual transmission was identified as the dominant mode of transmission, and particularly affected the community of men who have sex with men (MSM). This community experienced the highest incidence of Mpox cases, exacerbating the public health burden they already face due to the disproportionate impact of HIV. Given the simultaneous spread of HIV and Mpox within the MSM community, it is crucial to understand how these diseases interact. Specifically, since HIV is endemic within this population, understanding its influence on the spread and control of Mpox is essential. In this study, we analyze a mechanistic mathematical model of Mpox to explore the potential impact of HIV on the dynamics of Mpox within the MSM community. The model considered in this work incorporates the transmission dynamics of the two diseases, including antiretroviral therapy (ART) for HIV. We assumed that HIV was already endemic in the population at the onset of the Mpox outbreak. Through our analysis, we derived the Mpox invasion reproduction number within an HIV-endemic setting and established the existence and local asymptotic stability of the Mpox-free equilibrium under these conditions. Furthermore, we demonstrated the existence and local asymptotic stability of an Mpox-endemic equilibrium in an HIV-endemic regime. Notably, our findings revealed that the model exhibits a backward bifurcation, a phenomenon that may not have occurred in the absence of HIV within the population. The public health significance of our results is that the presence of HIV in the MSM community could hinder efforts to control Mpox, allowing the disease to become endemic even when its invasion reproduction number is below one. Additionally, we found that Mpox might be more challenging to control in scenarios where HIV increases susceptibility to Mpox. Finally, consistent with previous studies, our analysis confirms that reducing sexual contact can be effective for controlling the spread of Mpox within the MSM community.

Understanding the impact of HIV on mpox transmission in the MSM population: A mathematical modeling study

The recent mpox outbreak (in 2022-2023) has different clinical and epidemiological features compared with previous outbreaks of the disease. During this outbreak, sexual contact was believed to be the primary transmission route of the disease. In addition, the community of men having sex with men (MSM) was disproportionately affected by the outbreak. This population is also disproportionately affected by HIV infection. Given that both diseases can be transmitted sexually, the endemicity of HIV, and the high sexual behavior associated with the MSM community, it is essential to understand the effect of the two diseases spreading simultaneously in an MSM population. Particularly, we aim to understand the potential effects of HIV on an mpox outbreak in the MSM population. We develop a mechanistic mathematical model of HIV and mpox co-infection. Our model incorporates the dynamics of both diseases and considers HIV treatment with anti-retroviral therapy (ART). In addition, we consider a potential scenario where HIV infection increases susceptibility to mpox, and investigate the potential impact of this mechanism on mpox dynamics. Our analysis shows that HIV can facilitate the spread of mpox in an MSM population, and that HIV treatment with ART may not be sufficient to control the spread of mpox in the population. However, we showed that a moderate use of condoms or reduction in sexual contact in the population combined with ART is beneficial in controlling mpox transmission. Based on our analysis, it is evident that effective control of HIV, specifically through substantial ART use, moderate condom compliance, and reduction in sexual contact, is imperative for curtailing the transmission of mpox in an MSM population and mitigating the compounding impact of these intertwined epidemics.

Transmitted Antiretroviral Drug Resistance to Integrase Strand Transfer Inhibitors Class in São Paulo Metropolitan Area, Brazil

A newer integrase strand transfer inhibitor (INSTI) cabotegravir was recently approved for both therapy and prophylaxis and can play an essential role in the fight against AIDS. It shares similar resistance profile to dolutegravir, the cornerstone of Brazilian antiretroviral (ARV) treatment, with about 600 thousand people living with HIV in Brazil currently on regimens that contain this INSTI. Health services in the São Paulo metropolitan area are responsible for a large proportion of ARV dispensation in the country. Estimating transmitted drug resistance mutation (TDRM) in the area before cabotegravir introduction may provide a useful baseline information. Partial HIV-1 pol gene was sequenced (Sanger) from 192 newly diagnosed individuals from São Paulo and nearby cities (2020 to March 2023) at integrase, with 85 also at protease/reverse transcriptase regions. Retrotranscribed plasma RNA, amplified with nested PCR, was edited (Recall or Sequencher) and analyzed at Rega and Stanford db. Surveillance drug resistance mutations (SDRM) to INSTI class was detected in three cases (1.6%; 95% CI: 0.5%-5%), two E138K and one R263K, with 7.8% (95% CI: 5%-13%) with resistance mutations (major or accessory). SDRM for nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, and PI classes were identified in 7 (8.2% CI: 95% 4%-16%) cases. Subtype B predominated (69%), followed by subtype C (16%), now the second most prevalent infection in this area. Among 131 patients treated for over 6 months, 92% were virally suppressed below 200 copies/mL, with low TCD4 counts independently associated to failure. SDRM to INSTI class is rare in the area. Intermediate rates of transmitted resistance to other ARV classes are comparable to previous estimates. Viral suppression rates may depend on TCD4 counts, another negative impact of late diagnosis in care that deserves more attention.

Impact of screening and doxycycline prevention on the syphilis epidemic among men who have sex with men in British Columbia: a mathematical modelling study

Background

Men who have sex with men (MSM) in British Columbia (BC) are disproportionately affected by infectious syphilis and HIV. In this study, we developed a co-interaction model and evaluated the impact and effectiveness of possible interventions among different MSM subgroups on the syphilis epidemic.

Methods

We designed a deterministic compartmental model, which stratified MSM by HIV status and HIV pre-exposure prophylaxis (HIV-PrEP) usage into (1) HIV-negative/unaware MSM (HIV-PrEP not recommended, not on HIV-PrEP), (2) HIV-negative/unaware MSM with HIV-PrEP recommended (not on HIV-PrEP), (3) HIV-negative/unaware MSM actively on HIV-PrEP, and (4) MSM diagnosed with HIV. We estimated the effect of scaling up syphilis testing frequency from Status Quo to six-, four-, and three-months, increasing the percentage of MSM using doxycycline prevention (Doxy-P) to 25%, 50%, and 100% of the target level, and a combination of both among subgroups (2)-(4). We also assessed the impact of these interventions on the syphilis incidence rates from 2020 to 2034 in comparison to the Status Quo scenario where no intervention was introduced.

Findings

Under the Status Quo scenario, with the expansion of the HIV-PrEP program to improve syphilis testing, the syphilis incidence rate was estimated to peak at 16.1 [Credible Interval (CI):14.2-17.9] per 1,000 person-years (PYs) in 2023 and decrease to 6.7 (CI:3.8-10.9) per 1,000 PYs by 2034. The syphilis incidence rate in 2034 was estimated at 0.7 (0.3-1.3) per 1,000 PYs if MSM diagnosed with HIV could be tested every four months, and at 1.5 (0.7-3.0) per 1,000 PYs if HIV-negative/unaware MSM actively on HIV-PrEP could be tested every three months. By achieving 100% of the target coverage of Doxy-P, the syphilis incidence rate was estimated at 1.4 (0.5-3.4) if focusing on MSM diagnosed with HIV, and 2.6 (1.2-5.1) per 1,000 PYs if focusing on HIV-negative/unaware MSM actively on HIV-PrEP. Under the combined interventions, the syphilis incidence rate could be as low as 0.0 (0.0-0.1) and 0.8 (0.3-1.8) per 1,000 PYs, respectively.

Interpretation

The HIV-PrEP program in BC plays a crucial role in increasing syphilis testing frequency among high-risk MSM and reducing syphilis transmission among this group. In addition, introducing Doxy-P can be an effective complementary strategy to minimize syphilis incidence, especially among MSM diagnosed with HIV.

Funding

This work was funded by the Canadian Institutes of Health Research.

HIV pre-exposure prophylaxis (PrEP) should be free across Canada to those meeting evidence-based guidelines

HIV pre-exposure prophylaxis (PrEP) should be free across Canada for all those who meet evidence-based guidelines. PrEP is a highly effective tool for preventing HIV acquisition that has been approved for use in Canada since 2016. However, without public drug plans or private insurance, generic PrEP costs approximately $200 to $250 CAD monthly. Current PrEP programs across Canada are a confusing patchwork system with variability in coverage and prohibitive co-payments, making PrEP too expensive for many equity-deserving groups. However, publicly funded PrEP programs are demonstrated to be cost-effective and even cost-saving by reducing the long-term healthcare expenditures associated with managing HIV. PrEP is not just an individual-level clinical tool. It is a public health intervention. Alongside “treatment as prevention,” PrEP is an important population-level strategy for eliminating new HIV infections in Canada and can play a role in helping to address complex health inequities affecting communities highly affected by HIV. Navigating drug coverage for patients consumes time and resources among healthcare providers that could be spent helping to improve other social determinants of health. Affordability will remain the foremost barrier to PrEP access until PrEP is made free to all those who meet evidence-based guidelines.

Are Unequal Policies in Pre-Exposure Prophylaxis Uptake Needed to Improve Equality? An Examination Among Men Who Have Sex with Men in Los Angeles County

Racial and ethnic minority men who have sex with men (MSM) are disproportionately affected by HIV/AIDS in Los Angeles County (LAC), an important epicenter in the battle to end HIV. We examine tradeoffs between effectiveness and equality of pre-exposure prophylaxis (PrEP) allocation strategies among different racial and ethnic groups of MSM in LAC and provide a framework for quantitatively evaluating disparities in HIV outcomes. To do this, we developed a microsimulation model of HIV among MSM in LAC using county epidemic surveillance and survey data to capture demographic trends and subgroup-specific partnership patterns, disease progression, patterns of PrEP use, and patterns for viral suppression. We limit analysis to MSM, who bear most of the burden of HIV/AIDS in LAC. We simulated interventions where 3000, 6000, or 9000 PrEP prescriptions are provided annually in addition to current levels, following different allocation scenarios to each racial/ethnic group (Black, Hispanic, or White). We estimated cumulative infections averted and measures of equality, after 15 years (2021-2035), relative to base case (no intervention). By comparing allocation strategies on the health equality impact plane, we find that, of the policies evaluated, targeting PrEP preferentially to Black individuals would result in the largest reductions in incidence and disparities across the equality measures we considered. This result was consistent over a range of PrEP coverage levels, demonstrating that there are "win-win" PrEP allocation strategies that do not require a tradeoff between equality and efficiency.

Phylogenetic prioritization of HIV-1 transmission clusters with viral lineage-level diversification rates

Background and objectives

Public health officials faced with a large number of transmission clusters require a rapid, scalable and unbiased way to prioritize distribution of limited resources to maximize benefits. We hypothesize that transmission cluster prioritization based on phylogenetically derived lineage-level diversification rates will perform as well as or better than commonly used growth-based prioritization measures, without need for historical data or subjective interpretation.

Methodology

9822 HIV pol sequences collected during routine drug resistance genotyping were used alongside simulated sequence data to infer sets of phylogenetic transmission clusters via patristic distance threshold. Prioritized clusters inferred from empirical data were compared to those prioritized by the current public health protocols. Prioritization of simulated clusters was evaluated based on correlation of a given prioritization measure with future cluster growth, as well as the number of direct downstream transmissions from cluster members.

Results

Empirical data suggest diversification rate-based measures perform comparably to growth-based measures in recreating public heath prioritization choices. However, unbiased simulated data reveals phylogenetic diversification rate-based measures perform better in predicting future cluster growth relative to growth-based measures, particularly long-term growth. Diversification rate-based measures also display advantages over growth-based measures in highlighting groups with greater future transmission events compared to random groups of the same size. Furthermore, diversification rate measures were notably more robust to effects of decreased sampling proportion.

Conclusions and implications

Our findings indicate diversification rate-based measures frequently outperform growth-based measures in predicting future cluster growth and offer several additional advantages beneficial to optimizing the public health prioritization process.