Ross. D. Booton

Background: Characterising disparities in HIV infection across populations by gender, age, and HIV risk is key information to guide intervention priorities. We compared 9 models representing 15 different settings across Africa to assess how indicators measuring HIV acquisitions, transmissions, or potential long-term infections influence estimates of the contribution of different populations to new infections, including key populations (KPs, including female sex workers (FSW), their clients, men who have sex with men). Methods: We evaluated four indicators: I ₁ ) acquisition indicator measuring the annual fraction of all new infections acquired by a specific population, I ₂ ) direct transmission indicator measuring the annual fraction of all new infections directly transmitted by a specific population, I ₃ ) 1-year and I ₄ ) 10-year transmission population-attributable fractions ( tPAFs ). tPAFs measure the fraction of new infections averted if transmission involving a specific population was blocked over a specific time period. We compared estimates of the four indicators across 7 populations and 15 settings and assessed if the contribution of specific populations is ranked differently across indicators for 10 settings. Findings: Indicators identified distinct priority populations as the largest contributors: The acquisition indicator (I ₁ ) identified women aged 25+ years outside KPs as contributing the most to acquired infections in 8/10 settings in 2020, but to direct transmissions (I ₂ ) in only two settings. In 6/10 settings, the 10-year tPAFs (I ₄ ) identified non-KP men aged 25+ years and clients of FSW as the largest contributors to HIV transmission. Notably, non-KP women aged 15-24 years acquired (I ₁ ) more infections in 2020 (median of 1·7-fold across models) than they directly transmitted (I ₂ ), while non-KP men aged 25+ years and clients of FSWs transmitted more infections than they acquired in all but one model (median: 1·4 and 1·6-fold, respectively). Estimates of the 10-year tPAFs accounting for transmission in the long-term were substantially larger than the direct transmission indicator for all populations, especially for FSW (median: 2·0-fold). Interpretation: Indicators that reflect HIV acquisitions and transmissions over the short and long term can be utilised to capture the complexity of HIV epidemics across different populations and timeframes. The added nuance would improve the effectiveness of the HIV prevention response across all populations at risk. Funding: NIH, MRC. Research in context: Evidence before this study: Measures of the distribution of HIV acquisition across population groups are commonly used for assessing the contribution of populations to new HIV infections and prevention priorities. However, alternative indicators documented in the literature reflect transmissions or potential long-term effects. It is unclear how the choice of indicator affects the identification of populations that require additional prevention and treatment efforts to accelerate progress towards ending AIDS. We searched PubMed on March 08, 2025, with the terms (HIV) AND (Africa*) AND (acqui*) AND (transm*) AND (model*), with no language or publication date restriction, and identified no meta-assessment or mathematical model comparison studying differences in estimates of the fraction of all infections acquired and transmitted by a population when using different epidemiological indicators. Added value of this study: Using estimates from 9 models representing 15 different epidemic settings across Africa, we studied indicators of HIV epidemic contribution for 7 populations, including female sex workers, their clients, men who have sex with men, and non-key populations stratified by gender and age. We measured four commonly reported indicators of HIV contribution. One focused on acquired infections and the other three focused on transmissions. We found that estimates from these different indicators can differ greatly for the same model and population, to the extent that they identify different populations for prioritising interventions to accelerate HIV incidence declines. The acquisition-focused indicator (i.e. fraction of all infections acquired by a given population), the most used and communicated by UNAIDS, substantially underestimates the large contribution of men, and particularly male clients of female sex workers, to ongoing HIV transmission. Implications of all the available evidence: The choice of indicators measuring a population’s contribution to the HIV epidemic should be carefully considered and precisely defined. Modelling teams working in partnership with government, implementers, funders, and community members should systematically report both acquisition- and (long-term) transmission-focused indicators, instead of only measuring acquisitions in the short term as currently done. Multiple indicators will more comprehensively capture the potential impact of prevention efforts addressing acquisition and transmission risks of different vulnerable populations.

Objectives To perform a model-based cost-effectiveness evaluation of a rapid antimicrobial susceptibility test. Design A Markov model of a cohort of hospital inpatients with urinary tract infection (with inpatient numbers based on national administrative data from 1 April 2017 to 31 March 2019). Setting Urinary tract infections (UTI) in acute National Health Service (NHS) Trusts in England, from the perspective of the NHS Healthcare system, at a national level. Participants A simulated cohort of approximately 280 000 non-pregnant adult inpatients within secondary care with a clinical suspicion of UTI. Interventions Evaluation of the implementation of a fast bacterial impedance cytometry test (BICT) compared with current practice. Primary and secondary outcome measures Incremental cost, quality-adjusted life years, net monetary benefit, and bed days and appropriateness of antibiotic use per patient. Costs are presented in 2022 GBP. Results Considering benefits arising from reduced time on inappropriate treatment, BICT gives an average net monetary benefit (NMB) over the simulation period of approximately £4.3 million and dominates culture methods (from the healthcare system perspective and with a willingness to pay threshold of £20 000 per quality-adjusted life year). Total inappropriate prescribing days due to the BICT test are reduced by 57%. The extent of the benefit from BICT implementation was strongly dependent on prevalence of resistance, with the NMB increasing sevenfold to over £30 million in a high (40%) resistance prevalence scenario. At the population level, the patient groups with the highest cost and quality-adjusted life year impacts were 65–100-year-old females, followed by males, with uncomplicated UTIs. At an individual patient level, however, 16–64-year-old females with complicated UTIs with oral treatment, followed by 65–100-year-old males with complicated UTIs with oral treatment, were impacted to the greatest degree by the rapid BICT. Conclusions Under conservative assumptions and for wide parameter sensitivity, the implementation of BICT would be cost-effective from the NHS healthcare system perspective.

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.

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.

Introduction: Diagnoses of gonorrhoea in England rose by 26% between 2018 and 2019. Recent evidence that a vaccine against meningococcal B disease currently offered to infants in the UK (4CMenB) could additionally protect (with 31% efficacy) against gonorrhoea has led to renewed hope for a vaccine. A Phase 2 proof-of-concept trial of 4CMenB vaccination against gonorrhoea in adults is currently underway. Objectives: To investigate the potential public health impact of adolescent gonorrhoea vaccination in England, considering different implementation strategies. Methods: We developed a deterministic transmission-dynamic model of gonorrhoea infection among heterosexual 13–64-year-olds stratified by age, sex and sexual activity. We explored the impact of a National Immunisation Programme (NIP) among 14-year-olds for a vaccine with 31% efficacy, 6 years’ duration of protection, and 85% uptake. We also explored how impact might change for varying efficacy (20–50%) and uptake (75–95%), the addition of a catch-up programme, the use of boosters, and varying duration of protection. Results: An NIP against gonorrhoea could lead to 50,000 (95% credible interval, CrI 31,000-80,000) and 849,000 (95%CrI 476,000-1,568,000) gonorrhoea infections being averted over 10 and 70 years, respectively, in England, for a vaccine with 31% efficacy and 85% uptake. This is equivalent to 25% (95%CrI 17–33%) of heterosexual infections being averted over 70 years. Vaccine impact is predicted to increase over time and be greatest among 13–18-year-olds (39% of infections 95%CrI 31–49% averted) over 70 years. Varying vaccine efficacy and duration of protection had a noticeable effect on impact. Catch-up and booster vaccination increased the short- and long-term impact, respectively. Conclusions: A partially-effective vaccine against gonorrhoea infection, delivered to 14-year-olds alongside the MenACWY vaccine, could have an important population impact on gonorrhoea. Catch-up and booster vaccination could be considered alongside cohort vaccination to increase impact.

Objectives As most chlamydia cases are asymptomatic, regular testing and timely management may be necessary for control. We aimed to determine the preferences of people living in Hong Kong for chlamydia testing and management services. Methods An online panel of sexually active individuals living in Hong Kong completed the survey with two discrete choice experiments (DCEs). The first DCE examined the preferred attributes of a chlamydia testing service (cost, location, appointment time, speed of results, delivery of results and availability of other STI testing). The second DCE examined the preferred attributes of a chlamydia management service (cost, access to patient-delivered partner therapy, location, travel time, type of person consulted and attitude of staff). Results In total, 520 individuals participated: average age 36.8 years (SD 9.9), 40% males and 66% had a bachelor’s degree or higher. Choosing to test was most influenced by cost, followed by speed of results, delivery of results, extra STI testing, appointment available and the least important was the location of testing. Choosing to attend for management was most influenced by staff’s attitude, followed by cost, who they consult, access to patient-delivered partner therapy, travel time and the least important was treatment location. Conclusion To design effective chlamydia testing and management services, it is vital to respond to patient needs and preferences. For people living in Hong Kong, cost and staff attitude were the most important factors for deciding whether to test or be managed for chlamydia, respectively.

Introduction: The COVID‐19 pandemic is impacting HIV care globally, with gaps in HIV treatment expected to increase HIV transmission and HIV‐related mortality. We estimated how COVID‐19‐related disruptions could impact HIV transmission and mortality among men who have sex with men (MSM) in four cities in China, over a one‐ and five‐year time horizon.Methods: Regional data from China indicated that the number of MSM undergoing facility‐based HIV testing reduced by 59% during the COVID‐19 pandemic, alongside reductions in ART initiation (34%), numbers of all sexual partners (62%) and consistency of condom use (25%), but initial data indicated no change in viral suppression. A mathematical model of HIV transmission/treatment among MSM was used to estimate the impact of disruptions on HIV infections/HIV‐related deaths. Disruption scenarios were assessed for their individual and combined impact over one and five years for 3/4/6‐month disruption periods, starting from 1 January 2020.Results: Our model predicted new HIV infections and HIV‐related deaths would be increased most by disruptions to viral suppression, with 25% reductions (25% virally suppressed MSM stop taking ART) for a three‐month period increasing HIV infections by 5% to 14% over one year and deaths by 7% to 12%. Observed reductions in condom use increased HIV infections by 5% to 14% but had minimal impact (<1%) on deaths. Smaller impacts on infections and deaths (<3%) were seen for disruptions to facility HIV testing and ART initiation, but reduced partner numbers resulted in 11% to 23% fewer infections and 0.4% to 1.0% fewer deaths. Longer disruption periods (4/6 months) amplified the impact of disruption scenarios. When realistic disruptions were modelled simultaneously, an overall decrease in new HIV infections occurred over one year (3% to 17%), but not for five years (1% increase to 4% decrease), whereas deaths mostly increased over one year (1% to 2%) and five years (1.2 increase to 0.3 decrease).Conclusions: The overall impact of COVID‐19 on new HIV infections and HIV‐related deaths is dependent on the nature, scale and length of the various disruptions. Resources should be directed to ensuring levels of viral suppression and condom use are maintained to mitigate any adverse effects of COVID‐19‐related disruption on HIV transmission and control among MSM 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.

Objectives To develop a regional model of COVID-19 dynamics for use in estimating the number of infections, deaths and required acute and intensive care (IC) beds using the South West England (SW) as an example case. Design Open-source age-structured variant of a susceptible-exposed-infectious-recovered compartmental mathematical model. Latin hypercube sampling and maximum likelihood estimation were used to calibrate to cumulative cases and cumulative deaths. Setting SW at a time considered early in the pandemic, where National Health Service authorities required evidence to guide localised planning and support decision-making. Participants Publicly available data on patients with COVID-19. Primary and secondary outcome measures The expected numbers of infected cases, deaths due to COVID-19 infection, patient occupancy of acute and IC beds and the reproduction (‘R’) number over time. Results SW model projections indicate that, as of 11 May 2020 (when ‘lockdown’ measures were eased), 5793 (95% credible interval (CrI) 2003 to 12 051) individuals were still infectious (0.10% of the total SW population, 95% CrI 0.04% to 0.22%), and a total of 189 048 (95% CrI 141 580 to 277 955) had been infected with the virus (either asymptomatically or symptomatically), but recovered, which is 3.4% (95% CrI 2.5% to 5.0%) of the SW population. The total number of patients in acute and IC beds in the SW on 11 May 2020 was predicted to be 701 (95% CrI 169 to 1543) and 110 (95% CrI 8 to 464), respectively. The R value in SW was predicted to be 2.6 (95% CrI 2.0 to 3.2) prior to any interventions, with social distancing reducing this to 2.3 (95% CrI 1.8 to 2.9) and lockdown/school closures further reducing the R value to 0.6 (95% CrI 0.5 to 0.7). Conclusions The developed model has proved a valuable asset for regional healthcare services. The model will be used further in the SW as the pandemic evolves, and—as open-source software—is portable to healthcare systems in other geographies.

Introduction: The COVID-19 pandemic is impacting HIV care globally, with gaps in HIV treatment expected to increase HIV transmission and HIV-related mortality. We estimated how COVID-19-related disruptions could impact HIV transmission and mortality among men who have sex with men (MSM) in four cities in China. Methods: Regional data from China indicated that the number of MSM undergoing facility-based HIV testing reduced by 59% during the COVID-19 pandemic, alongside reductions in ART initiation (34%), numbers of sexual partners (62%) and consistency of condom use (25%). A deterministic mathematical model of HIV transmission and treatment among MSM in China was used to estimate the impact of these disruptions on the number of new HIV infections and HIV-related deaths. Disruption scenarios were assessed for their individual and combined impact over 1 and 5 years for a 3-, 4- or 6-month disruption period. Results: Our China model predicted that new HIV infections and HIV-related deaths would be increased most by disruptions to viral suppression, with 25% reductions for a 3-month period increasing HIV infections by 5-14% over 1 year and deaths by 7-12%. Observed reductions in condom use increased HIV infections by 5-14% but had minimal impact (<1%) on deaths. Smaller impacts on infections and deaths (<3%) were seen for disruptions to facility testing and ART initiation, but reduced partner numbers resulted in 11-23% fewer infections and 0.4-1.0% fewer deaths. Longer disruption periods of 4 and 6 months amplified the impact of combined disruption scenarios. When all realistic disruptions were modelled simultaneously, an overall decrease in new HIV infections was always predicted over one year (3-17%), but not over 5 years (1% increase-4% decrease), while deaths mostly increased over one year (1-2%) and 5 years (1.2 increase – 0.3 decrease). Conclusions: The overall impact of COVID-19 on new HIV infections and HIV-related deaths is dependent on the nature, scale and length of the various disruptions. Resources should be directed to ensuring levels of viral suppression and condom use are maintained to mitigate any adverse effects of COVID-19 related disruption on HIV transmission and control among MSM in China.