The Impact of Treatment as Prevention on the HIV Epidemic in British Columbia, Canada

Longitudinal evolution of the HIV effective reproduction number following sequential expansion of treatment as prevention and pre-exposure prophylaxis in British Columbia, Canada: a population-level programme evaluation

BACKGROUND

Treatment as prevention and pre-exposure prophylaxis (PrEP) are key strategies in the control of HIV/AIDS. We aimed to characterise the longitudinal effects of antiretroviral therapy (ART), followed by treatment as prevention and the addition of PrEP, on the HIV effective reproduction number (Re) in British Columbia, Canada.

METHODS

This population-level programme evaluation used data from the Drug Treatment Program of the British Columbia Centre for Excellence in HIV/AIDS (Vancouver, British Columbia, Canada). We also used estimates of HIV incidence and prevalence from the Public Health Agency of Canada, data on the number of new HIV diagnoses per year from the British Columbia Centre for Disease Control, and mortality data from the British Columbia Vital Statistics Agency. Data were obtained from 1985 until 2022, depending on the database source. Outcomes were the annual HIV prevalence, HIV incidence, number of new HIV diagnoses, number of people living with HIV on ART, HIV/AIDS-related and all-cause mortality rates, the HIV incidence-to-all-cause-mortality ratio, and Re. We calculated the modified effective reproduction number (Rme) using two thresholds of viral suppression and compared these values with Re.

FINDINGS

We found a 95% decline in HIV/AIDS-related mortality and a 91% decrease in HIV incidence over the study period. The Re progressively declined from 1996 to 2022; however, from 1996 to 2017, Rme remained stable (>1) when calculated for people living with HIV with unsuppressed viraemia, suggesting that treatment as prevention reduces HIV incidence by decreasing the pool of individuals who are potentially able to transmit the virus. From 2018 to 2022, a decline in the estimated Re and Rme (<1) was observed regardless of whether we considered all people living with HIV or only those who were virologically unsuppressed. This finding suggests that PrEP decreases HIV incidence by reducing the number of susceptible individuals in the community, independently of viral suppression.

INTERPRETATION

Our results show the synergy between generalised treatment as prevention and targeted PrEP in terms of decreasing HIV incidence. These findings support the incorporation of longitudinal monitoring of Re at a programmatic level to identify opportunities for the optimisation of treatment-as-prevention and PrEP programmes.

FUNDING

British Columbia Ministry of Health, Health Canada, Public Health Agency of Canada, Vancouver Coastal Health, Vancouver General Hospital Foundation, Genome British Columbia, and the Canadian Institutes of Health Research.

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.

Improved outcomes following gastrointestinal surgery among people living with HIV in the HAART-era: A scoping review

BACKGROUND

This study aimed to review the varied 1-4 gastrointestinal (GI) system surgical outcomes among people living with Human Immunodeficiency Virus (PLWH) in the HAART-era.

METHODS

MEDLINE and EMBASE were searched for primary publications on GI surgery outcomes exclusively in HAART-treated HIV patients. NSQIP-reported complications (NRCs), all-cause complications (ACC) and HIV disease parameters were extracted.

RESULTS

12 studies met study inclusion criteria, examining bowel (4), bariatric (5), cholecystectomy (1), appendectomy (1), and other general abdominal operations (1). The NRC rate was 0%, ≥44.4% and 13.3% in bariatric, bowel and appendix surgeries, respectively. Over half of NRCs were infectious. HAART-treated patients had lower ACC, LOS, and sepsis versus untreated-HIV, and higher ACC, LOS and reoperation rates versus HIV-negative patients.

CONCLUSION

HAART use is associated with markedly improved NRC outcomes post GI surgery among PLWH; however, these remained inferior to those documented among HIV uninfected individuals.

It's all about connection: Determinants of social support and the influence on HIV treatment interruptions among people living with HIV in British Columbia, Canada

BACKGROUND

Social support has previously been found to be associated with improved health outcomes of individuals managing chronic illnesses, including amongst people living with HIV (PLWH). For women and people who use injection drugs who continue to experience treatment disparities in comparison to other PLWH, social support may have potential in facilitating better treatment engagement and retention. In this analysis, we examined determinants of social support as measured by the Medical Outcomes Study - Social Support Survey (MOS-SSS) scale, and quantified the relationship between MOS-SSS and HIV treatment interruptions (TIs) among PLWH in British Columbia, Canada.

METHODS

Between January 2016 and September 2018, we used purposive sampling to enroll PLWH, 19 years of age or older living in British Columbia into the STOP HIV/AIDS Program Evaluation study. Participants completed a baseline survey at enrolment which included the MOS-SSS scale, where higher MOS-SSS scores indicated greater social support. Multivariable linear regression modeled the association between key explanatory variables and MOS-SSS scores, whereas multivariable logistic regression modeled the association between MOS-SSS scores and experiencing TIs while controlling for confounders.

RESULTS

Among 644 PLWH, we found that having a history of injection drug use more than 12 months ago but not within the last 12 months, self-identifying as Indigenous, and sexual activity in the last 12 months were positively associated with MOS-SSS, while being single, divorced, or dating (vs. married), experiences of lifetime violence, and diagnosis of a mental health disorder were inversely associated. In a separate multivariable model adjusted for gender, ethnicity, recent homelessness, sexual activity in the last 12 months, and recent injection drug use, we found that higher MOS-SSS scores, indicating more social support, were associated with a lower likelihood of HIV treatment interruptions (adjusted odds ratio: 0.90 per 10-unit increase, 95% confidence interval: 0.83, 0.99).

CONCLUSIONS

Social support may be an important protective factor in ensuring HIV treatment continuity among PLWH. Future research should examine effective means to build social support among communities that have potential to promote increased treatment engagement.

Disability-adjusted life years associated with chronic comorbidities among people living with and without HIV: Estimating health burden in British Columbia, Canada

Life span of people living with HIV (PLWH) has increased dramatically with the advent of modern antiretroviral therapy. As a result, comorbidities have emerged as a significant concern in this population. To describe the burden of chronic comorbidities among PLWH and HIV-negative individuals in British Columbia (BC), Canada, we estimated disability-adjusted life years (DALYs) related to these comorbidities. Based on a population-based cohort in BC, antiretroviral-treated adult PLWH and 1:4 age-sex-matched HIV-negative controls were followed for ≥1 year during 2001-2012. DALYs combined years of life lost to premature mortality (YLLs) and due to disability (YLDs), and were estimated following the Global Burden of Diseases' approaches. DALYs associated with non-AIDS-defining cancers, diabetes, osteoarthritis, hypertension, dementia, cardiovascular (CVD), kidney, liver and chronic obstructive pulmonary diseases were each measured for 2008-2012. Among PLWH, DALYs attributed to non-AIDS-related cancers were also estimated for 2013-2020. We observed that at baseline, our matched cohort consisted of 82% males with a median age of 40 years (25th-75th percentiles: 34-47). During 2008-2012, 7042 PLWH and 30,640 HIV-negative individuals were alive, where PLWH experienced a twofold higher DALYs associated with chronic comorbidities (770.2 years/1000 people [95% credible intervals: 710.2, 831.6] vs. 359.0 [336.0, 382.2]). Non-AIDS-defining cancers and CVD contributed the highest DALYs in both populations, driven by YLLs rather than YLDs. Among PLWH, we estimated increasing DALYs attributable to non-AIDS-defining cancers with 91.7 years/1000 people (77.4, 106.0) in 2013 vs. 97.6 (81.0, 115.2) in 2020. In this study, we showed that PLWH experience a disproportionate burden of chronic comorbidities compared to HIV-negative individuals. The observed disparities may relate to differential health behaviors, residual HIV-related inflammation, and ART-related toxicities. As aging shapes future healthcare needs, our findings highlight the need to enhance prevention and management of comorbidities as part of HIV care.

Healthcare and treatment experiences among people diagnosed with HIV before and after a province-wide treatment as prevention initiative in British Columbia, Canada

Introduction

In 2010, the Canadian province of British Columbia (BC) initiated the Seek and Treat for Optimal Prevention of HIV/AIDS (STOP HIV/AIDS) program to improve HIV testing, linkage to care, and treatment uptake, thereby operationalizing the HIV Treatment as Prevention (TasP) framework at the population-level. In this analysis, we evaluated self-reported HIV care experiences and therapeutic outcomes among people diagnosed with HIV prior to and after implementation of this provincial program.

Methods

A cross-sectional analysis was performed on the baseline data of a cohort of people living with HIV (PLWH) (19 years and older) in the province of BC sampled from July 2016 to September 2018. All participants consented to linking their survey data to the provincial HIV treatment registry. Individuals diagnosed with HIV from January 1 2000—December 31 2009 were classified as pre-intervention and those diagnosed January 1 2010—December 31 2018 as post-intervention cohorts. Bivariate analyses were run using Chi-square and Wilcoxon Rank Sum tests. Cox proportional hazards regression model demonstrates time to antiretroviral therapy (ART) initiation (from HIV baseline) and virological suppression (2 consecutive plasma viral load measurements < 200 copies/ml).

Results

Of the 325 participants included in this analysis, 198 (61%) were diagnosed with HIV in the pre-intervention era and 127 (39%) in the post-intervention era. A higher proportion of participants in post-intervention era were diagnosed at walk-in clinics (45% vs. 39%) and hospitals (21% vs. 11%) (vs pre-intervention) (p = 0.042). Post-intervention participants had initiated ART with less advanced HIV disease (CD4 count 410 vs. 270 cells/ul; p = 0.001) and were less likely to experience treatment interruptions at any point in the 5 years after HIV diagnosis (17% vs. 48%; p < 0.001). The post-intervention cohort had significantly more timely ART initiation (aHR: 5.97, 95%CI 4.47, 7.97) and virologic suppression (aHR: 2.03, 95%CI 1.58, 2.60) following diagnosis, after controlling for confounders.

Conclusions

We found favourable treatment experiences and more timely ART initiation and virologic suppression after a targeted TasP provincial program. Our results illustrate the importance of accessible low-barrier HIV testing and treatment in tackling the HIV epidemic.

Mucocutaneous Manifestations of People Living with HIV in Current Antiretroviral Therapy Era

OBJECTIVE

It has been reported that approximately 90% of patients who are infected with human immunodeficiency virus (HIV) have various cutaneous symptoms that are related to the virus. This study aims to describe the cutaneous disorders that have developed in HIV-infected patients and to investigate the factors that may be related, such as relationships to drug use and CD4 counts.

METHODS

This cross-sectional study included people who were living with HIV and being followed by our hospital's infectious diseases clinic after they had been referred to the dermatology clinic because of skin lesions. These patients had been diagnosed with HIV by enzyme-linked immunosorbent assay tests and were included in the study if they were older than 18 years and had agreed to participate. Findings from detailed dermatological examinations were recorded, along with the patients' CD4 counts, the durations of their illnesses, and the treatments they received.

RESULTS

144 patients were included in the study. The most common mucocutaneous manifestation was seborrheic dermatitis, at 28.5% (n = 41). The mean CD4 count was 607.1 (min-max = 10.6-1982).The CD4 counts were divided into three groups in the study as follows: 22 (15.3%) patients with <200, 35 (24.3%) patients between 200 and 500, and 87 (60.4%) patients with >500. There were no statistical differences between these groups in terms of dermatological findings. Nevertheless, the highest rate of patients with three or more dermatological conditions was found among those with CD4 counts <200 (n = 11.50%).

CONCLUSION

Skin manifestations are common in patients who are HIV-positive; however, many skin disorders can be seen in HIV/acquired immunodeficiency syndrome (AIDS) patients whatever CD4 cell counts of these patients are.

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.

A province-wide HIV initiative to accelerate initiation of treatment-as-prevention and virologic suppression in British Columbia, Canada: a population-based cohort study

BACKGROUND

In 2010, HIV treatment as prevention (TasP), encompassing widespread HIV testing and immediate initiation of free antiretroviral treatment (ART), was piloted under the Seek and Treat for Optimal Prevention of HIV/AIDS initiative (STOP) in British Columbia, Canada. We compared the time from HIV diagnosis to treatment initiation, and from treatment initiation to first virologic suppression, before (2005-2009) and after (2010-2016) the implementation of STOP.

METHODS

In this population-based cohort study, we used longitudinal data of all people living with an HIV diagnosis in BC from 1996 to 2017. We included those aged 18 years or older who had never received ART and had received an HIV diagnosis in the 2005-2016 period. We defined the virologic suppression date as the first date of at least 2 consecutive test results within 4 months with a viral load of less than 200 copies/mL. Negative binomial regression models assessed the effect of STOP on the time to ART initiation and suppression, adjusting for confounders. All p values were 2-sided, and we set the significance level at 0.05.

RESULTS

Participants who received an HIV diagnosis before STOP (n = 1601) were statistically different from those with a diagnosis after STOP (n = 1700); 81% versus 84% were men (p = 0.0187), 30% versus 15% had ever injected drugs (p < 0.0001), and 27% versus 49% had 350 CD4 cells/μL or more at diagnosis (p < 0.0001). The STOP initiative was associated with a 64% shorter time from diagnosis to treatment (adjusted mean ratio 0.36, 95% confidence interval [CI] 0.34-0.39) and a 21% shorter time from treatment to suppression (adjusted mean ratio 0.79, 95% CI 0.73-0.85).

INTERPRETATION

In a population with universal health coverage, a TasP intervention was associated with shorter times from HIV diagnosis to treatment initiation, and from treatment initiation to viral suppression. Our results show accelerating progress toward the United Nations' 90-90-90 target of people with HIV who have a diagnosis, those who are on antiretroviral therapy and those who are virologically suppressed, and support the global expansion of TasP to accelerate the control of HIV/AIDS.

Concordance of HIV transmission risk factors elucidated using viral diversification rate and phylogenetic clustering

Background and objectives

Although HIV sequence clustering is routinely used to identify subpopulations experiencing elevated transmission, it over-simplifies transmission dynamics and is sensitive to methodology. Complementarily, viral diversification rates can be used to approximate historical transmission rates. Here, we investigated the concordance and sensitivity of HIV transmission risk factors identified by phylogenetic clustering, viral diversification rate, changes in viral diversification rate and a combined approach.

Methodology

Viral sequences from 9848 people living with HIV in British Columbia, Canada, sampled between 1996 and February 2019, were used to infer phylogenetic trees, from which clusters were identified and viral diversification rates of each tip were calculated. Factors associated with heightened transmission risk were compared across models of cluster membership, viral diversification rate, changes in diversification rate, and viral diversification rate among clusters.

Results

Viruses within larger clusters had higher diversification rates and lower changes in diversification rate than those within smaller clusters; however, rates within individual clusters, independent of size, varied widely. Risk factors for both cluster membership and elevated viral diversification rate included being male, young, a resident of health authority E, previous injection drug use, previous hepatitis C virus infection or a high recent viral load. In a sensitivity analysis, models based on cluster membership had wider confidence intervals and lower concordance of significant effects than viral diversification rate for lower sampling rates.

Conclusions and implications

Viral diversification rate complements phylogenetic clustering, offering a means of evaluating transmission dynamics to guide provision of treatment and prevention services.

Lay Summary

Understanding HIV transmission dynamics within clusters can help prioritize public health resource allocation. We compared socio-demographic and clinical risk factors associated with phylogenetic cluster membership and viral diversification rate, a historical branching rate, in order to assess their relative concordance and sampling sensitivity.

Longitudinal Analysis of HIV Risk and Substance Use Patterns for Men Who Have Sex with Men and Women and Men Who Have Sex with Men Only

Men Who Have Sex with Men and Women (MSMW) experience discrimination from same-sex and heterosexual communities partially because of perceptions they feature high-risk sexual behavior, elevated polysubstance use levels, and constitute an HIV bridge population. We used a longitudinal multivariate generalized linear mixed model comparing sexual risk and substance use patterns for Men Who Have Sex with Men Only (MSMO) with MSMW in the same cohort study. Data consisted of 771 men reporting 3,705 sexual partnerships from 2012-2017. For high-risk sexual behavior multivariate results showed non-significant (p>0.05) differences for partner number and commercial sex work, and significantly less (p<0.05) HIV prevalence and condomless anal sex. However, MSMW had significantly higher levels of hallucinogen and prescription opioid use, and substance treatment histories. Only one HIV-positive MSMW had a transmittable viral load, negating the concept of an HIV bridge population. Results indicate the need for additional longitudinal studies comparing MSMO and MSMW.

Disparities in multimorbidity and mortality among people living with and without HIV across British Columbia's health regions: a population-based cohort study

OBJECTIVES

Longer survival has increased the likelihood of antiretroviral-treated people living with HIV (PLWH) developing age-associated comorbidities. We compared the burden of multimorbidity and all-cause mortality across HIV status in British Columbia (BC), and assessed the longitudinal effect of multimorbidity on all-cause mortality among PLWH.

METHODS

Antiretroviral-treated PLWH aged ≥19 years and 1:4 age-sex-matched HIV-negative individuals from a population-based cohort were followed for ≥1 year during 2001-2012. Diagnoses of seven age-associated comorbidities were identified from provincial administrative databases and grouped into 0, 1, 2, and ≥3 comorbidities. Multimorbidity prevalence and age-standardized mortality rates (ASMRs) in both populations were stratified by BC's health regions. Marginal structural models were used to estimate the effect of multimorbidity on mortality among PLWH, adjusted for time-varying confounders affected by prior multimorbidity.

RESULTS

Among 8031 PLWH and 32,124 HIV-negative individuals, 25% versus 11% developed multimorbidity, and 23.53 deaths/1000 person-years (95% confidence interval [95% CI]: 22.02-25.13) versus 3.04 (2.81-3.29) were observed, respectively. PLWH in Northern region had the highest ASMR, but those in South Vancouver Island experienced the greatest difference in mortality compared with HIV-negative individuals. Among PLWH, compared with those with zero comorbidities, adjusted hazard ratios for those with 1, 2, and ≥3 comorbidities were 3.36 (95% CI: 2.86-3.95), 6.92 (5.75-8.33), and 12.87 (10.45-15.85), respectively.

CONCLUSION

PLWH across BC's health regions experience excess multimorbidity and associated mortality. We highlight health disparities which are key when planning the distribution of healthcare resources across BC, and provide evidence for improved HIV care models integrating prevention and management of chronic diseases.

Overdose mortality is reducing the gains in life expectancy of antiretroviral-treated people living with HIV in British Columbia, Canada

BACKGROUND

A remarkable reduction in AIDS-related mortality has been achieved through the widespread use of triple combination antiretroviral therapy, considerably increasing the life expectancy of people living with HIV (PLWH). However, these survival gains are now at risk in North America due to an unprecedented public health emergency: the deadly drug overdose epidemic. Drug overdoses are now the leading cause of unintentional death in British Columbia (BC), Canada and the United States due to synthetic opioids (e.g., fentanyl) in illegal markets. This manuscript aimed to estimate the effect of overdose mortality on life expectancy and identify covariates associated with the hazard for overdose mortality in the presence of competing risk among PLWH in BC.

METHODS

Those eligible were aged ≥20 years, initiated antiretroviral therapy from 1-Apr-1996 to 30-Dec-2017, and were followed until 31-Dec-2017, last contact or death date. We estimated the potential gains in life expectancy from abridged life tables. We modelled the association between covariates and the cause-specific hazard for overdose mortality, accounting for mortality of other causes as a competing risk.

RESULTS

Among the 10,362 PLWH, 3% experienced overdose mortality. The life expectancy at age 20 increased by 8.7 years from 2002-2007 to 2008-2013 compared to only 3.0 years from 2008-2013 to 2014-2017. The potential gain in life expectancy was 3.3 years at age 20 during the ongoing overdose epidemic (2014-2017). There were gender differences in life expectancies throughout the study period. People who have ever injected drugs, women and viral load monitoring non-compliance were key covariates associated with an increased hazard of overdose mortality.

CONCLUSION

Survival gains among PLWH have been considerably reduced due to the ongoing overdose epidemic.

Estimation of time of HIV seroconversion using a modified CD4 depletion model

Introduction

Several methods have been proposed to estimate the time of HIV seroconversion, including those based on CD4 cell depletion models. However, previous models have failed to consider the heterogeneity that exists in CD4 trajectories among different sub-populations. Our objective was to estimate the time from HIV seroconversion relative to the HIV diagnosis date in a population-based cohort of people living with HIV (PLWH) in the province of British Columbia, Canada.

Methods

We used linked administrative and clinical data from the British Columbia Seek and Treat for Optimal Prevention of HIV/AIDS (STOP HIV/AIDS) cohort, which contains longitudinal individual-level data on all PLWH ever diagnosed in the province. Eligible participants were aged ≥18 years and diagnosed with HIV between 1989 and 2013. The outcome was pre-antiretroviral treatment CD4 cell count measurements assessed every six months. Models were stratified by age and stage of HIV infection at diagnosis. Several explanatory variables were considered including longitudinal viral load measurements. Longitudinal CD4, square root transformed, was modeled via a non-linear mixed effects model; time was modeled using an exponential decay function. We assumed a Gaussian distribution (identity link), an AR(1) correlation structure, and a random intercept and slope for the longitudinal viral load measurements. Due to the population variation in CD4 count among uninfected individuals, we assumed 500 to 1500 cells/mm³ as the normal range when estimating the time of HIV seroconversion.

Results

Longitudinal data on 1,253 individuals were analysed: 80% male, 33% White, and the median age at diagnosis was 38 years (25^th-75^th percentile [Q₁-Q₃], 31 to 45). CD4 decay differed by stage of infection at diagnosis and age, with those ≥50 years in Stages 1 and 2 experiencing a faster decline in CD4 over time. The median duration of infection from seroconversion until HIV diagnosis was 6.9 (Q₁-Q₃, 3.9 to 10.1) years.

Conclusions

Considering the heterogeneity that exists in individual CD4 cell trajectories in a population, we presented a methodology that only relies on routinely collected HIV-related data, which can be further extended to estimate other epidemic measures.

Implementation opportunities and challenges identified by key stakeholders in scaling up HIV Treatment as Prevention in British Columbia, Canada: a qualitative study

Background

The province of British Columbia (BC), Canada, was among the first jurisdictions to scale up HIV Treatment as Prevention (TasP) to the population level, including funding and policy commitments that enhanced HIV testing efforts (e.g., expansion of routine, opt-out testing), while also making antiretroviral therapy universally available to all people living with HIV. As such, BC represents a critical context within which to identify factors that influenced the scalability of TasP (e.g., acceptability, adoption, fidelity, equitable reach, sustainability), including key opportunities and challenges.

Methods

We draw on in-depth, semi-structured interviews with 10 key stakeholders, comprised policymakers at the local and provincial levels and representatives from community-based organizations. Using the Consolidated Framework for Implementation Research (CFIR) to guide data collection, coding, and analysis, we identified key factors that influenced practice transformation and scale up.

Results

Key factors that contributed to the successful scale up of TasP included: (i) opportunities that enhanced stakeholder buy-in based on features of the intervention characteristics, including with regard to assessments about the quality and strength of evidence supporting TasP; (ii) an inner setting implementation climate that was, in part, shaped by the large and highly symbolic government investments into TasP; (iii) features of the outer setting such as external policies (e.g., harm reduction) that cultivated opportunities to implement new "systems-level" approaches to HIV intervention; (iv) the personal attributes of some "middle-level" influencers, including a team that was comprised of some highly motivated and social justice-oriented individuals (e.g., folks who were deeply committed to serving marginalized populations); and (v) the capacity to develop various implementation processes that could maintain "nimble and evidence-informed" adaptations across a highly decentralized service delivery system, while also creating opportunities to adapt features of TasP programming based on "real time" program data.

Conclusion

Constructs across all five domains of CFIR (intervention characteristics, outer setting, inner setting, characteristics of individuals, and process) were identified to influence the success of TasP in BC. Our findings provide important insights into how BC can successfully implement and scale up other systems-level interventions that have demonstrated efficacy, while also offering insights for other jurisdictions that are currently or planning to scale up TasP.