Medicine (RMH) - Research Publications
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ItemNo Preview AvailableMathematical analysis of a two-strain disease model with amplification(PERGAMON-ELSEVIER SCIENCE LTD, 2021-02)
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ItemNo Preview AvailableModeling the Cost-Effectiveness of Latent Tuberculosis Screening and Treatment Strategies in Recent Migrants to a Low-Incidence Setting(OXFORD UNIV PRESS INC, 2022-01-24)Many tuberculosis (TB) cases in low-incidence settings are attributed to reactivation of latent TB infection (LTBI) acquired overseas. We assessed the cost-effectiveness of community-based LTBI screening and treatment strategies in recent migrants to a low-incidence setting (Australia). A decision-analytical Markov model was developed that cycled 1 migrant cohort (≥11-year-olds) annually over a lifetime from 2020. Postmigration/onshore and offshore (screening during visa application) strategies were compared with existing policy (chest x-ray during visa application). Outcomes included TB cases averted and discounted cost per quality-adjusted life-year (QALY) gained from a health-sector perspective. Most recent migrants are young adults and cost-effectiveness is limited by their relatively low LTBI prevalence, low TB mortality risks, and high emigration probability. Onshore strategies cost at least $203,188 (Australian) per QALY gained, preventing approximately 2.3%-7.0% of TB cases in the cohort. Offshore strategies (screening costs incurred by migrants) cost at least $13,907 per QALY gained, preventing 5.5%-16.9% of cases. Findings were most sensitive to the LTBI treatment quality-of-life decrement (further to severe adverse events); with a minimal decrement, all strategies caused more ill health than they prevented. Additional LTBI strategies in recent migrants could only marginally contribute to TB elimination and are unlikely to be cost-effective unless screening costs are borne by migrants and potential LTBI treatment quality-of-life decrements are ignored.
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ItemUnderstanding how Victoria, Australia gained control of its second COVID-19 wave(NATURE PORTFOLIO, 2021-11-01)During 2020, Victoria was the Australian state hardest hit by COVID-19, but was successful in controlling its second wave through aggressive policy interventions. We calibrated a detailed compartmental model of Victoria's second wave to multiple geographically-structured epidemic time-series indicators. We achieved a good fit overall and for individual health services through a combination of time-varying processes, including case detection, population mobility, school closures, physical distancing and face covering usage. Estimates of the risk of death in those aged ≥75 and of hospitalisation were higher than international estimates, reflecting concentration of cases in high-risk settings. We estimated significant effects for each of the calibrated time-varying processes, with estimates for the individual-level effect of physical distancing of 37.4% (95%CrI 7.2-56.4%) and of face coverings of 45.9% (95%CrI 32.9-55.6%). That the multi-faceted interventions led to the dramatic reversal in the epidemic trajectory is supported by our results, with face coverings likely particularly important.
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ItemAre We Better-Off? The Benefits and Costs of Australian COVID-19 Lockdown(FRONTIERS MEDIA SA, 2021-12-02)
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ItemTreatment outcomes in patients with multidrug-resistant tuberculosis in north-west Ethiopia(WILEY, 2017-03)OBJECTIVE: Multidrug-resistant tuberculosis (MDR-TB) is an emerging public health problem in Ethiopia. The aim of this study was to assess MDR-TB treatment outcomes and determine predictors of poor treatment outcomes in north-west Ethiopia. METHODS: A retrospective cohort study was conducted using all MDR-TB patients who were enrolled at Gondar University Hospital since the establishment of the MDR-TB programme in 2010. A Cox proportional hazard model was used to identify the predictors of time to poor treatment outcomes, which were defined as death or treatment failure. RESULTS: Of the 242 patients who had complete records, 131 (54%) were cured, 23 (9%) completed treatment, 31 (13%) died, four (2%) experienced treatment failure, 27 (11%) were lost to follow-up, six (2%) transferred out, and 20 (8%) were still on treatment at the time of analysis. The overall cumulative probability survival of the patients at the end of treatment (which was 24 months in duration) was 80% (95% CI: 70%, 87%). The proportion of patients with poor treatment outcomes increased over time from 6% per person-year (PY) during 2010-2012, to 12% per PY during 2013-2015. The independent predictors of time to poor treatment outcome were being anaemic [AHR = 4.2; 95% CI: 1.1, 15.9] and being a farmer [AHR = 2.2; 95% CI: 1.0, 4.9]. CONCLUSIONS: Overall, in north-west Ethiopia, the MDR-TB treatment success rate was high. However, poor treatment outcomes have gradually increased since 2012. Being a farmer and being anaemic were associated with poor treatment outcomes. It would be beneficial to assess other risk factors that might affect treatment outcomes such as co-infection with malaria, poverty and other socio-economic and biological risk factors.
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ItemNo Preview AvailableVaccines and variants: Modelling insights into emerging issues in COVID-19 epidemiology(ELSEVIER SCI LTD, 2021-09)Mathematical modelling has played a pivotal role in understanding the epidemiology of and guiding public health responses to the ongoing coronavirus disease of 2019 (COVID-19) pandemic. Here, we review the role of epidemiological models in understanding evolving epidemic characteristics, including the effects of vaccination and Variants of Concern (VoC). We highlight ways in which models continue to provide important insights, including (1) calculating the herd immunity threshold and evaluating its limitations; (2) verifying that nascent vaccines can prevent severe disease, infection, and transmission but may be less efficacious against VoC; (3) determining optimal vaccine allocation strategies under efficacy and supply constraints; and (4) determining that VoC are more transmissible and lethal than previously circulating strains, and that immune escape may jeopardize vaccine-induced herd immunity. Finally, we explore how models can help us anticipate and prepare for future stages of COVID-19 epidemiology (and that of other diseases) through forecasts and scenario projections, given current uncertainties and data limitations.
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ItemUnderstanding COVID-19 dynamics and the effects of interventions in the Philippines: A mathematical modelling study(ELSEVIER, 2021-09)BACKGROUND: COVID-19 initially caused less severe outbreaks in many low- and middle-income countries (LMIC) compared with many high-income countries, possibly because of differing demographics, socioeconomics, surveillance, and policy responses. Here, we investigate the role of multiple factors on COVID-19 dynamics in the Philippines, a LMIC that has had a relatively severe COVID-19 outbreak. METHODS: We applied an age-structured compartmental model that incorporated time-varying mobility, testing, and personal protective behaviors (through a "Minimum Health Standards" policy, MHS) to represent the first wave of the Philippines COVID-19 epidemic nationally and for three highly affected regions (Calabarzon, Central Visayas, and the National Capital Region). We estimated effects of control measures, key epidemiological parameters, and interventions. FINDINGS: Population age structure, contact rates, mobility, testing, and MHS were sufficient to explain the Philippines epidemic based on the good fit between modelled and reported cases, hospitalisations, and deaths. The model indicated that MHS reduced the probability of transmission per contact by 13-27%. The February 2021 case detection rate was estimated at ~8%, population recovered at ~9%, and scenario projections indicated high sensitivity to MHS adherence. INTERPRETATION: COVID-19 dynamics in the Philippines are driven by age, contact structure, mobility, and MHS adherence. Continued compliance with low-cost MHS should help the Philippines control the epidemic until vaccines are widely distributed, but disease resurgence may be occurring due to a combination of low population immunity and detection rates and new variants of concern.
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ItemRisk factors for multidrug-resistant tuberculosis in northwest Ethiopia: A case-control study(WILEY-HINDAWI, 2019-07)Ethiopia is one of 30-high burden multidrug-resistant tuberculosis (MDR-TB) countries globally. The aim of this study was to describe the characteristics of patients with MDR-TB and to investigate risk factors for MDR-TB relative to having drug-susceptible tuberculosis (TB), in northwest Ethiopia. A hospital-based, unmatched case-control study was conducted. Cases were all MDR-TB patients (i.e., resistant to at least rifampicin and isoniazid) who were confirmed by culture and drug-susceptibility testing whilst enrolled on treatment at Gondar University Hospital. Controls were all drug-susceptible tuberculosis (DS-TB) patients who were confirmed by Gene Xpert MTB/RIF at Gondar University Hospital. Univariable and multivariable logistic regression models were used for comparisons, and odds ratios with 95% confidence intervals (CI) were computed to measure the strength of association between the dependent and independent variables. A total of 452 patients (242 MDR-TB and 210 DS-TB) were included in this study. The mean age of the study participants was 33 years (SD ± 14 years). Approximately one-fifth (78, 17%) of all study participants were human immunodeficiency virus (HIV) positive; 21% (51) of cases and 13% (27) of controls. Risk factors associated with MDR-TB were a history of previous TB treatment (Adjusted Odds Ratio (AOR): 83.8; 95% CI: 40.7, 172.5), low educational status (AOR: 5.32; 95% CI: 1.43, 19.81); and ages less than 20 years (AOR: 9.01; 95% CI: 2.30, 35.25) and 21-30 years (AOR: 2.61; 95% CI: 1.02, 6.64). HIV infection was also significantly associated with MDR-TB among new TB patients (AOR: 5.55; 95% CI: 1.17, 26.20). This study shows that clinical and demographic features can be used to indicate higher risks of drug resistance in this setting.
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ItemTreatment access is only the first step to hepatitis C elimination: experience of universal anti-viral treatment access in Australia(WILEY, 2019-05)BACKGROUND: Global targets to eliminate hepatitis C (HCV) might be met by sustained treatment uptake. AIM: To describe factors facilitating HCV treatment uptake and potential challenges to sustaining treatment levels after universal access to direct-acting anti-virals (DAA) across Australia. METHODS: We analysed national Pharmaceutical Benefits Scheme data to determine the number of DAA prescriptions commenced before and after universal access from March 2016 to June 2017. We inferred facilitators and barriers to treatment uptake, and challenges that will prevent local and global jurisdictions reaching elimination targets. RESULTS: In 2016, 32 877 individuals (14% of people living with HCV in Australia) commenced HCV DAA treatment, and 34 952 (15%) individuals commenced treatment in the first year of universal access. Treatment uptake peaked at 13 109 DAA commencements per quarter immediately after universal access, but more than halved (to 5320 in 2017 Q2) within 12 months. General practitioners have written 24% of all prescriptions but with a significantly increased proportion over time (9% in 2016 Q1 to 37% in 2017 Q2). In contrast, hepatology or infectious diseases specialists have written a declining share from 74% to 38% during the same period. General practitioners provided a greater proportion (47%) of care in regional/remote areas than major cities. CONCLUSIONS: Broad treatment access led to rapid initial increases in treatment uptake, but this uptake has not been sustained. Our results suggest achieving global elimination targets requires more than treatment availability: people with HCV need easy access to testing and linkage to care in community settings employing a diverse prescriber base.
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ItemSIRCLE: a randomised controlled cost comparison of self-administered short-course isoniazid and rifapentine for cost-effective latent tuberculosis eradication(WILEY, 2017-12)BACKGROUND: Currently, treatment of latent tuberculosis infection (LTBI) in Australia consists most commonly of a 9-month course of isoniazid (9H). A 3-month course of weekly isoniazid and rifapentine (3HP) has been shown to be as effective as 9 months of daily isoniazid, and associated with less hepatotoxicity; however, rifapentine is not currently available in Australia. Introduction of this regimen would have apparent advantages for people with LTBI in Victoria by safely shortening duration of LTBI therapy. However, the cost benefit of this new therapeutic approach is uncertain. AIM: Cost-analysis of standard and short-course therapy for LTBI in an Australian context. METHODS: Single-centre randomised controlled trial conducted between December 2013-March 2016. Participants underwent 1:1 randomisation to either a 9-month course of daily isoniazid or a 12-week course of weekly isoniazid and rifapentine. The primary outcome measure was total healthcare system costs (in Australian dollars; AUD) per completed course of LTBI therapy. Secondary cost analyses were performed to consider varying assumptions regarding commercial cost of rifapentine. RESULTS: Overall, 34 of 40 (85%) participants in the 9H group and 36/40 (90%) in the 3HR group completed therapy. One patient in the 3HP group was hospitalised for a febrile illness; no hospitalisations were recorded in the 9H group. The cost per completed course of 9H was 601 AUD, while that of 3HP was significantly lower at 511 AUD (P < 0.01). CONCLUSIONS: This study provides cost analysis evidence to support the use of 3HP for the treatment of LTBI in Australia.