Review of mathematical models of Neisseria gonorrhoeae vaccine impact: Implications for vaccine development.

An effective prophylactic vaccine for prevention of Neisseria gonorrhoeae infection would have a major impact on sexual and reproductive health worldwide. Interest in developing gonorrhoea vaccines is growing due to the reported high rates of N. gonorrhoeae infections globally, and the threat of antimicrobial resistance. Several gonorrhoea vaccine candidates are currently under evaluation and various mathematical models have been used to assess the potential population-level impact a gonorrhoea vaccine may have once available. Here we review key aspects of gonorrhoea vaccine mathematical modelling studies, including model structures, populations considered, and assumptions used as well as vaccine characteristics and implementation scenarios investigated. The predicted vaccine impact varied between studies, ranging from as little as ∼17 % reduction in N. gonorrhoeae prevalence after 30 years up to 100 % reduction after 5 years. However, all studies predicted that even a partially effective gonorrhoea vaccine could have a substantial impact in reducing N. gonorrhoeae prevalence or incidence, particularly when high coverage is achieved within either important risk groups or the overall sexually active population. As expected, higher vaccine efficacy against acquisition of N. gonorrhoeae and longer duration of protection were linked to greater reductions in infections. A vaccine that alters onward transmission could also substantially reduce infections. Several gaps and research needs have been identified by researchers in the field and via this narrative literature review. For example, future modelling to inform gonorrhoea vaccine development and implementation should consider additional populations that are at high risk of N. gonorrhoeae infection, especially in low- and middle-income settings, as well as the impact of vaccination on the potential adverse sexual and reproductive health outcomes of infection. In addition, more detailed and robust epidemiological, biological, and behavioural data is needed to enable more accurate and robust modelling of gonorrhoea vaccine impact to inform future scientific and public health decision-making.

The potential impact of a vaccine on Neisseria gonorrhoeae prevalence among heterosexuals living in a high prevalence setting.

BACKGROUND: Treatment of Neisseria gonorrhoeae is under threat with the emergence and spread of antimicrobial resistance. Thus, there is a growing interest in the development of a gonorrhoea vaccine. We used mathematical modelling to assess the impact of a hypothetical vaccine in controlling gonorrhoea among heterosexuals living in a setting of relatively high N. gonorrhoeae prevalence (∼3 %). METHODS: We developed a mathematical model of N. gonorrhoeae transmission among 15-49-year-old heterosexuals, stratified by age and sex, and calibrated to prevalence and sexual behaviour data from South Africa as an example of a high prevalence setting for which we have data available. Using this model, we assessed the potential impact of a vaccine on N. gonorrhoeae prevalence in the entire population. We considered gonorrhoea vaccines having differing impacts on N. gonorrhoeae infection and transmission and offered to different age-groups. RESULTS: The model predicts that N. gonorrhoeae prevalence can be reduced by ∼50 % in 10 years following introduction of a vaccine if annual vaccination uptake is 10 %, vaccine efficacy against acquisition of infection is 25 % and duration of protection is 5 years, with vaccination available to the entire population of 15-49-year-olds. If only 15-24-year-olds are vaccinated, the predicted reduction in prevalence in the entire population is 25 % with equivalent vaccine characteristics and uptake. Although predicted reductions in prevalence for vaccination programmes targeting only high-activity individuals and the entire population are similar over the same period, vaccinating only high-activity individuals is more efficient as the cumulative number of vaccinations needed to reduce prevalence in the entire population by 50 % is ∼3 times lower for this programme. CONCLUSION: Provision of a gonorrhoea vaccine could lead to substantial reductions in N. gonorrhoeae prevalence in a high prevalence heterosexual setting, even with moderate annual vaccination uptake of a vaccine with partial efficacy.

The changing epidemiology of Neisseria gonorrhoeae genogroups and antimicrobial resistance in Queensland, Australia, 2010-15: a case series analysis of unique Neisseria gonorrhoeae isolates.

BACKGROUND: Neisseria gonorrhoeae (NG) can lead to serious reproductive and sexual health outcomes, and the annual number of NG notifications in Australia increased steadily from 10329 in 2010 to 29549 by 2020. Australian populations most affected are urban men who have sex with men and First Nations peoples living in remote areas, and a resurgence in urban heterosexuals has been observed since 2012. METHODS: A case series analysis of Queensland NG isolates (2010-15) exploring temporal trends and antimicrobial resistance by demographic and geographic distribution and genotype was performed. Proportions describe age, sex, strain, genogroup (NG multi-antigen sequence typing), region, swab site, antimicrobial sensitivity and isolate rates per 100000 population. Dominant genogroups were identified. RESULTS: Among 3953 isolates, the median age was 25years (IQR 20-34years) and most (n =2871/3915, 73%) were men. Brisbane city (68.8) and Far North Queensland (54.1) excluding Cairns showed the highest rates. Forty-six genogroups were documented, seven (G2992, G6876, G1415, G4186, G5, G1407 and G6937) comprised half of all isolates. The predominant male genogroup was G2992 (16%), and G6876 (20%) for females; G5 was predominantly male from 2010 to 2011, but equal in both sexes from 2012 to 2015. CONCLUSION: Considerable temporal, geographical and demographical diversity was observed in Queensland NG isolates, which has public health implications. Certain genogroups are more transient than others, and evidence suggests bridging from male-dominant networks to heterosexual networks. Molecular surveillance can enhance tracking the epidemiology and movement of NG in Australia, highlighting the necessity of genotyping to expose potentially prevalent strains circulating in undetected or underrepresented networks by current screening methods.

Assessing the Impact of HIV Preexposure Prophylaxis Scale-Up on Gonorrhea Incidence Among Gay and Bisexual Men in Sydney: A Mathematical Modeling Study.

BACKGROUND: The rollout of preexposure prophylaxis (PrEP) for HIV prevention among gay and bisexual men (GBM) is associated with increases in condomless anal intercourse, potentially increasing the incidence of other sexually transmissible infections (STIs). METHODS: We developed an individual-based mathematical model to simulate the transmission of Neisseria gonorrhoeae among GBM in Sydney, accounting for changes in sexual practices, STI testing, and PrEP use. We calibrated and validated the model using reported incidence rates for HIV-positive and HIV-negative GBM from 2010 to 2019. Scenarios were run with varying PrEP uptake, PrEP-related STI testing, and PrEP-related sexual behavior and testing intervals up to 2030 to assess the impact of PrEP use on gonorrhea incidence. RESULTS: Preexposure prophylaxis uptake and associated 3-monthly STI testing from 2015 onward resulted in a predicted increase from 20 to 37 N. gonorrhoeae infections per 100 person-years among HIV-negative GBM by the end of 2020. This is lower than the counterfactual predictions of 45 per 100 person-years if PrEP were not scaled up and 48 per 100 person-years with nonadherence to 3-monthly STI testing. Increasing the time between STI tests for PrEP users by 1 month from 2018 results in the incidence rate among HIV-negative GBM increasing by 8% by 2030. If PrEP coverage doubles from 24% to 53%, incidence among HIV-negative GBM declines by ~25% by 2030. CONCLUSIONS: Behavior change due to widespread PrEP use may lead to significant increases in gonorrhea incidence in GBM, but the recommended quarterly STI testing recommended for PrEP users should reduce incidence by 18% by 2030.

Impact of Testing Strategies to Combat a Major Syphilis Outbreak Among Australian Aboriginal and Torres Strait Islander Peoples: A Mathematical Modeling Study.

Background: A syphilis outbreak among Australian Aboriginal and Torres Strait Islander people (respectfully referred to as Aboriginal) has resulted in almost 4000 notifications by 2020, with several congenital syphilis cases and infant deaths. Outbreak control efforts became coordinated under a National enhanced test and treat response in 2017. We evaluated the impact of these efforts and of expansion of testing interventions on syphilis prevalence. Methods: We developed an individual-based mathematical model of infectious syphilis transmission among young heterosexual Aboriginal people aged 15-34 years living in and moving between regional and remote areas, and we assessed the impact of existing and hypothetical outbreak control responses on syphilis prevalence. Results: The increased testing coverage achieved through the response (from 18% to 39% over 2011-2020) could stabilize the epidemic from 2021. To return to pre-outbreak prevalence (<0.24%) by 2025, testing coverage must reach 60%. The addition of annual community-wide screening, where 30% of youth in communities are tested over 6 weeks, would reduce prevalence to the pre-outbreak level within 4 years. If testing coverage had been scaled-up to 60% at the start of outbreak in mid-2011, the outbreak would have been mitigated. Conclusions: Our results suggest that to control the syphilis outbreak, the response needs to be delivered to enable the maximum coverage of testing to be reached in the shortest time to reduce the prevalence to pre-outbreak levels. Reduction could be hastened with community-wide screening at similar time periods across all communities together with increases in annual testing coverage.

A Gonococcal Vaccine Has the Potential to Rapidly Reduce the Incidence of Neisseria gonorrhoeae Infection Among Urban Men Who Have Sex With Men.

BACKGROUND: A gonococcal vaccine is urgently needed due to increasing gonorrhea incidence and emerging multidrug-resistant gonococcal strains worldwide. Men who have sex with men (MSM) have among the highest incidences of gonorrhea and may be a key target population for vaccination when available. METHODS: An individual-based, anatomical site-specific mathematical model was used to simulate Neisseria gonorrhoeae transmission in a population of 10 000 MSM. The impact of vaccination on gonorrhea prevalence was assessed. RESULTS: With a gonococcal vaccine of 100% or 50% protective efficacy, gonorrhea prevalence could be reduced by 94% or 62%, respectively, within 2 years if 30% of MSM are vaccinated on presentation for sexually transmitted infection (STI) testing. Elimination of gonorrhea is possible within 8 years with vaccines of ≥ 50% efficacy lasting 2 years, providing a booster vaccination is available every 3 years on average. A vaccine's impact may be reduced if it is not effective at all anatomical sites. CONCLUSIONS: Our study indicates that with a vaccine of modest efficacy and an immunization strategy that targets MSM presenting for STI screening, the prevalence of gonorrhea in this population could be rapidly and substantially reduced.

Modelling response strategies for controlling gonorrhoea outbreaks in men who have sex with men in Australia.

The ability to treat gonorrhoea with current first-line drugs is threatened by the global spread of extensively drug resistant (XDR) Neisseria gonorrhoeae (NG) strains. In Australia, urban transmission is high among men who have sex with men (MSM) and importation of an XDR NG strain in this population could result in an epidemic that would be difficult and costly to control. An individual-based, anatomical site-specific mathematical model of NG transmission among Australian MSM was developed and used to evaluate the potential for elimination of an imported NG strain under a range of case-based and population-based test-and-treat strategies. When initiated upon detection of the imported strain, these strategies enhance the probability of elimination and reduce the outbreak size compared with current practice (current testing levels and no contact tracing). The most effective strategies combine testing targeted at regular and casual partners with increased rates of population testing. However, even with the most effective strategies, outbreaks can persist for up to 2 years post-detection. Our simulations suggest that local elimination of imported NG strains can be achieved with high probability using combined case-based and population-based test-and-treat strategies. These strategies may be an effective means of preserving current treatments in the event of wider XDR NG emergence.

Genital warts trends in Australian and overseas-born people in Australia: A cross-sectional trend analysis to measure progress towards control and elimination.

Background: Substantial declines in genital warts have been observed in countries with quadrivalent/nonavalent human papillomavirus (q/n HPV) vaccination programmes, with Australia showing the most pronounced and long-term reductions. No study has assessed progress towards elimination of genital warts in a nation-wide sample of patients, and migrants' contribution to population-level control of genital warts. We assessed Australia's progress towards genital warts elimination by examining trends in diagnoses in Australian- and overseas-born patients of sexual health clinics (SHCs) across Australia. Methods: A cross-sectional trend analysis of new genital warts diagnoses among first-time patients of 34 SHCs, between 2004 and 2018, was performed. Rate ratios (RR) were calculated using Poisson regression models, for comparing trends in proportions of new genital warts diagnoses in Australian- and overseas-born patients during the pre-vaccination era (2004-2007) and the vaccination era (2008-2018), and by 2018 relative to 2004-2007. Findings: A total of 439,957 new patients (Australian-born: 230,230; overseas-born: 209,727) were seen at SHCs, 6•4% were diagnosed with genital warts (Australian-born: 7•1%; overseas-born: 5•6%). By 2018, there had been a 64% reduction in the proportion of all SHC patients with a genital warts diagnosis relative to 2004-2007 (RR: 0•36, 95% CI: 0•35-0•38). The decline was more pronounced at 72% (RR: 0•28, 95% CI: 0 •27-0•30) among Australian-born patients, with the greatest reduction in women and men aged <21 years, at 98% (RR: 0•02, 95% CI: 0•01-0•03) and 92% (RR: 0•08, 95% CI: 0•06-0•11), respectively. By 2018, there was a 49% reduction in the proportion of overseas-born patients diagnosed with genital warts (RR: 0•51, 95% CI:0•48-0•54), and a 21% reduction in overseas-born patients from countries with no or bivalent HPV (bHPV) vaccination programme (RR: 0•79, 95% CI: 0•71-0•90). Interpretation: The substantial reductions in Australian-born people is a testament to the efficacy of quadrivalent (qHPV) and nonavalent (nHPV) vaccines and the high and wide-spread vaccination coverage in Australia. However, population-wide elimination of genital warts in Australia is dependent on other countries initiating or expanding their own HPV vaccination programmes. Funding: The Australian Government Department of Health and Seqirus Australia.

Modelling testing and response strategies for COVID-19 outbreaks in remote Australian Aboriginal communities.

BACKGROUND: Remote Australian Aboriginal and Torres Strait Islander communities have potential to be severely impacted by COVID-19, with multiple factors predisposing to increased transmission and disease severity. Our modelling aims to inform optimal public health responses. METHODS: An individual-based simulation model represented SARS-CoV2 transmission in communities ranging from 100 to 3500 people, comprised of large, interconnected households. A range of strategies for case finding, quarantining of contacts, testing, and lockdown were examined, following the silent introduction of a case. RESULTS: Multiple secondary infections are likely present by the time the first case is identified. Quarantine of close contacts, defined by extended household membership, can reduce peak infection prevalence from 60 to 70% to around 10%, but subsequent waves may occur when community mixing resumes. Exit testing significantly reduces ongoing transmission. Concurrent lockdown of non-quarantined households for 14 days is highly effective for epidemic control and reduces overall testing requirements; peak prevalence of the initial outbreak can be constrained to less than 5%, and the final community attack rate to less than 10% in modelled scenarios. Lockdown also mitigates the effect of a delay in the initial response. Compliance with lockdown must be at least 80-90%, however, or epidemic control will be lost. CONCLUSIONS: A SARS-CoV-2 outbreak will spread rapidly in remote communities. Prompt case detection with quarantining of extended-household contacts and a 14 day lockdown for all other residents, combined with exit testing for all, is the most effective strategy for rapid containment. Compliance is crucial, underscoring the need for community supported, culturally sensitive responses.

Effect on genital warts in Australian female and heterosexual male individuals after introduction of the national human papillomavirus gender-neutral vaccination programme: an analysis of national sentinel surveillance data from 2004-18.

BACKGROUND: In Australia, the government-funded human papillomavirus (HPV) vaccination programme was introduced in April, 2007, for girls and young women, and in February, 2013, for boys. As of Dec 31, 2018, all Australian-born female individuals younger than 38 years and male individuals younger than 21 years have been eligible for the free quadrivalent or nonavalent HPV vaccine. We aimed to examine the trends in genital wart diagnoses among Australian-born female and heterosexual male individuals who attended sexual health clinics throughout Australia before and after the introduction of the gender-neutral HPV vaccination programme in February, 2013. METHODS: We did a serial cross-sectional analysis of genital wart diagnoses among Australian-born female and heterosexual male individuals attending a national surveillance network of 35 clinics between Jan 1, 2004, and Dec 31, 2018. We calculated prevalence ratios of genital warts, using log-binomial regression models, for the female-only vaccination period (July 1, 2007, to Feb 28, 2013), gender-neutral vaccination period (March 1, 2013, to Dec 31, 2018), and the whole vaccination period (July 1, 2007, to Dec 31, 2018) compared with the pre-vaccination period (Jan 1, 2004, to June 30, 2007). FINDINGS: We included 121 038 men and 116 341 women in the analysis. Overall, we observed a 58% reduction (prevalence ratio 0·42, 95% CI 0·40-0·44) in genital wart diagnoses in female individuals and a 45% reduction (0·55, 0·53-0·57) in genital wart diagnoses in heterosexual male individuals after the introduction of the vaccination programme in 2007. The largest reduction in genital warts was observed in younger individuals, and there was a decreasing magnitude of reduction with increasing age (80%, 72%, 61%, 41%, and 16% reductions in female individuals aged 15-20 years, 21-25 years, 26-30 years, 31-35 years, and ≥36 years, respectively; 70%, 61%, 49%, 37%, and 29% reductions in male individuals aged 15-20 years, 21-25 years, 26-30 years, 31-35 years, and ≥36 years, respectively). Significant reductions observed in female individuals (0·32, 0·28-0·36) and male individuals (0·51, 0·43-0·61) aged 15-20 years in the female-only vaccination period were followed by a more substantial reduction in female individuals (0·07, 0·06-0·09) and male individuals (0·11, 0·08-0·15) aged 15-20 years in the gender-neutral vaccination period. INTERPRETATION: The national gender-neutral HPV vaccination programme has led to substantial and ongoing reduction in genital warts among Australian female and heterosexual male individuals, with a marked reduction in young individuals who received the vaccine at school. FUNDING: Seqirus Australia and the Australian Government Department of Health.

Azithromycin or Doxycycline for Asymptomatic Rectal Chlamydia trachomatis.

BACKGROUND: Rectal chlamydia is a common bacterial sexually transmissible infection among men who have sex with men. Data from randomized, controlled trials are needed to guide treatment. METHODS: In this double-blind trial conducted at five sexual health clinics in Australia, we randomly assigned men who have sex with men and who had asymptomatic rectal chlamydia to receive doxycycline (100 mg twice daily for 7 days) or azithromycin (1-g single dose). Asymptomatic chlamydia was selected as the trial focus because more than 85% of men with rectal chlamydia infection are asymptomatic, and clinical guidelines recommend a longer treatment course for symptomatic infection. The primary outcome was a negative nucleic acid amplification test for rectal chlamydia (microbiologic cure) at 4 weeks. RESULTS: From August 2016 through August 2019, we enrolled 625 men (314 in the doxycycline group and 311 in the azithromycin group). Primary outcome data were available for 290 men (92.4%) in the doxycycline group and 297 (95.5%) in the azithromycin group. In the modified intention-to-treat population, a microbiologic cure occurred in 281 of 290 men (96.9%; 95% confidence interval [CI], 94.9 to 98.9) in the doxycycline group and in 227 of 297 (76.4%; 95% CI, 73.8 to 79.1) in the azithromycin group, for an adjusted risk difference of 19.9 percentage points (95% CI, 14.6 to 25.3; P<0.001). Adverse events that included nausea, diarrhea, and vomiting were reported in 98 men (33.8%) in the doxycycline group and in 134 (45.1%) in the azithromycin group (risk difference, -11.3 percentage points; 95% CI, -19.5 to -3.2). CONCLUSIONS: A 7-day course of doxycycline was superior to single-dose azithromycin in the treatment of rectal chlamydia infection among men who have sex with men. (Funded by the National Health and Medical Research Council; RTS Australian New Zealand Clinical Trials Registry number, ACTRN12614001125617.).

Defining Elimination of Genital Warts-A Modified Delphi Study.

Background: Substantial declines in genital warts (GW) have been observed in countries with quadrivalent HPV vaccination programmes, with Australia showing the highest reductions due to early commencement and high vaccination coverage. There is a real potential to achieve GW elimination; however, no GW elimination definition exists. Taking Australia as a case study, we aimed to reach expert consensus on a proposed GW elimination definition using a modified Delphi process. Method: We used modelling and epidemiological data to estimate the expected number of new GW cases, from pre-vaccination (baseline) in 2006 to the year 2060 in Australian heterosexuals, men who have sex with men (MSM), and newly arrived international travellers and migrants. We used these data and the literature, to develop a questionnaire containing ten elimination-related items, each with 9-point Likert scales (1-strongly disagree; 9-strongly agree). The survey was completed by 18 experts who participated in a full day face-to-face modified Delphi study, in which individuals and then small groups discussed and scored each item. The process was repeated online for items where consensus (≥70% agreement) was not initially achieved. Median and coefficient of variation (COV) were used to describe the central tendency and variability of responses, respectively. Findings: There was a 95% participation rate in the face-to-face session, and 84% response rate in the final online round. The median item score ranged between 7.0 and 9.0 and the COV was ≤0.30 on all items. Consensus was reached that at ≥80% HPV vaccination coverage, GW will be eliminated as a public health problem in Australia by 2060. During this time period there will be a 95% reduction in population-level incidence compared with baseline, equivalent to <1 GW case per 10,000 population. The reductions will occur most rapidly in Australian heterosexuals, with 73%, 90% and 97% relative reductions by years 2021, 2030 and 2060, respectively. The proportion of new GW cases attributable to importation will increase from 3.6% in 2006 to ~49% in 2060. Interpretation: Our results indicate that the vaccination programme will minimise new GW cases in the Australian population, but importation of cases will continue. This is the first study to define GW elimination at a national level. The framework developed could be used to define GW elimination in other countries, with thresholds particularly valuable for vaccination programme impact evaluation. Funding: LK supported through an Australian Government Research Training Programme Scholarship; unconditional funding from Seqirus to support the Delphi Workshop.

Factors Associated With Early Resumption of Condomless Anal Sex Among Men Who Have Sex With Men After Rectal Chlamydia Treatment.

BACKGROUND: The resumption of sexual activity shortly after commencing treatment for sexually transmitted infections (STIs) is poorly described despite contributing to onward transmission. With azithromycin remaining an option for rectal Chlamydia trachomatis, resuming sex too early after treatment may contribute to antimicrobial resistance because of exposure of newly acquired STIs to subinhibitory concentrations. METHODS: Clinical and sexual behavioral data were collected from men participating in a trial assessing treatment efficacy for rectal chlamydia. Data were collected at recruitment and weekly for 3 weeks after commencing treatment. Outcome measures were resumption of any sexual activity or condomless receptive anal sex within 1, 2, or 3 weeks after commencing treatment. Generalized linear regression was used to calculate adjusted risk ratios (aRR) to identify associated factors. RESULTS: Almost 1 in 10 men (9.5%; 95% confidence interval [CI], 7.2-12.1) resumed condomless receptive anal sex within 1 week of commencing treatment. This was associated with current preexposure prophylaxis use (aRR, 3.4; 95% CI, 2.5-4.8]) and having 9 or more sexual partners in the last 3 months (aRR, 3.2; 95% CI, 1.6-5.0). Most men (75.0%; 95% CI, 71.3-78.5) resumed any sexual activity within 3 weeks; this was associated with a greater number of sexual partners (4-8 partners; aRR, 1.2; 95% CI, 1.1-1.5; ≥9 partners; aRR, 1.5; 95% CI, 1.3-1.7). CONCLUSIONS: Resuming condomless receptive anal sex early after treatment may facilitate onward transmission and promote antimicrobial resistance for STIs. Although azithromycin remains a treatment option, this analysis highlights the need for new health promotion messages regarding early resumption of sex and continued surveillance for antimicrobial resistance.

Prevalence of human papillomavirus in teenage heterosexual males following the implementation of female and male school-based vaccination in Australia: 2014-2017.

BACKGROUND: Australia introduced a school-based human papillomavirus (HPV) vaccination program for females aged 12-13 years in 2007, with a three-year catch-up to age 26; and for boys aged 12-13 from 2013, with a two-year catch-up to age 15. This study aimed to compare the prevalence of penile HPV between teenage heterosexual males in cohorts eligible or non-eligible for the school-based male vaccination program. METHODS: Between 2014 and 2017, sexually active heterosexual males aged 17-19 were recruited from sexual health centres and community sources across Australia. Males provided a self-collected penile swab for 37 HPV genotypes using Roche Linear Array and completed a questionnaire. We calculated adjusted prevalence ratios (aPR) of HPV between males in two periods: 2014-2015 (preceding implementation of school-based male vaccination) and 2016-2017 (eligible for school-based male vaccination). Self-reported vaccine doses were confirmed with doses reported to the National HPV Vaccination Program Register. RESULTS: Overall, 152 males were recruited in 2014-2015 and 146 in 2016-2017. Numbers of female sex partners and condom use did not differ between the two periods. The prevalence of quadrivalent vaccine-preventable [4vHPV] genotypes (6/11/16/18) was low in both periods (2.6% [2014-15] versus 0.7% [2016-17]; p = 0.371; aPR 0.28 [95% CI: 0.03-2.62]). Compared with men in 2014-2015, men in 2016-2017 had a lower prevalence of any of the 37 HPV genotypes tested (21.7% versus 11.6%; aPR 0.62 [95% CI: 0.36-1.07]) and any of the 13 high-risk genotypes tested (15.8% versus 7.5%; aPR 0.59 [95% CI: 0.30-1.19]). Prevalence of low-risk HPV genotypes did not differ between the two periods. Of the males recruited in 2016-2017, 55% had received ≥1 vaccine dose. CONCLUSION: The prevalence of 4vHPV genotypes among teenage heterosexual males in both cohorts was low, presumably due to herd protection from the female-only vaccination program. Further studies are required to determine the impact of universal HPV vaccination on HPV prevalence in males.

A systematic review of scabies transmission models and data to evaluate the cost-effectiveness of scabies interventions.

BACKGROUND: Scabies is a common dermatological condition, affecting more than 130 million people at any time. To evaluate and/or predict the effectiveness and cost-effectiveness of scabies interventions, disease transmission modelling can be used. OBJECTIVE: To review published scabies models and data to inform the design of a comprehensive scabies transmission modelling framework to evaluate the cost-effectiveness of scabies interventions. METHODS: Systematic literature search in PubMed, Medline, Embase, CINAHL, and the Cochrane Library identified scabies studies published since the year 2000. Selected papers included modelling studies and studies on the life cycle of scabies mites, patient quality of life and resource use. Reference lists of reviews were used to identify any papers missed through the search strategy. Strengths and limitations of identified scabies models were evaluated and used to design a modelling framework. Potential model inputs were identified and discussed. FINDINGS: Four scabies models were published: a Markov decision tree, two compartmental models, and an agent-based, network-dependent Monte Carlo model. None of the models specifically addressed crusted scabies, which is associated with high morbidity, mortality, and increased transmission. There is a lack of reliable, comprehensive information about scabies biology and the impact this disease has on patients and society. DISCUSSION: Clinicians and health economists working in the field of scabies are encouraged to use the current review to inform disease transmission modelling and economic evaluations on interventions against scabies.

Modelling the in-host dynamics of Neisseria gonorrhoeae infection.

The bacterial species Neisseria gonorrhoeae (NG) has evolved to replicate effectively and exclusively in human epithelia, with its survival dependent on complex interactions between bacteria, host cells and antimicrobial agents. A better understanding of these interactions is needed to inform development of new approaches to gonorrhoea treatment and prevention but empirical studies have proven difficult, suggesting a role for mathematical modelling. Here, we describe an in-host model of progression of untreated male symptomatic urethral infection, including NG growth and interactions with epithelial cells and neutrophils, informed by in vivo and in vitro studies. The model reproduces key observations on bacterial load and clearance and we use multivariate sensitivity analysis to refine plausible ranges for model parameters. Model variants are also shown to describe mouse infection dynamics with altered parameter ranges that correspond to observed differences between human and mouse infection. Our results highlight the importance of NG internalisation, particularly within neutrophils, in sustaining infection in the human model, with ∼80% of the total NG population internalised from day 25 on. This new mechanistic model of in-host NG infection dynamics should also provide a platform for future studies relating to antimicrobial treatment and resistance and infection at other anatomical sites.

Modelling the decline and future of hepatitis A transmission in Australia.

Hepatitis A incidence has declined in most countries through a combination of prevention measures, augmented through the use of a highly effective vaccine. In Australia, the proportion of the population susceptible to hepatitis A infection has declined over time due to high rates of opportunistic vaccination as well as the sustained inflow of seropositive immigrants from high-endemicity countries. These factors have contributed to a rapid decline in incidence. An age-structured hepatitis A transmission model incorporating demographic changes was fitted to seroprevalence and disease notification data and used to project incidence trends and transmission potential for hepatitis A in the general population. Robustness of findings was assessed through worst-case scenarios regarding vaccine uptake, migration and the duration of immunity. The decline in age-specific seroprevalence until the introduction of hepatitis A vaccine in 1994 was well explained through a declining basic reproduction number (R0 ) that remained >1. Accounting for existing immunity, we estimated that the effective reproduction number (Reff ) <1 in the general population of Australia since the early 1990s, declining more rapidly after the introduction of the hepatitis A vaccine. Future projections under a variety of scenarios support Reff remaining <1 with continued low incidence in the general population. In conclusion, our results suggest that sustained endemic transmission in the general Australian population is no longer possible although risks of sporadic outbreaks remain. This suggests potential for local elimination of hepatitis A infection in Australia, provided that elimination criteria can be defined and satisfied in risk groups. The methodology used here to investigate elimination potential can easily be replicated in settings such as in the USA where sequential seroprevalence studies are supported by routine notification data.

Molecular point-of-care testing for chlamydia and gonorrhoea in Indigenous Australians attending remote primary health services (TTANGO): a cluster-randomised, controlled, crossover trial.

BACKGROUND: Timely diagnosis and treatment of sexually transmissible infections will prevent morbidity and onward transmission. We aimed to assess the efficacy of a point-of-care molecular test for Chlamydia trachomatis and Neisseria gonorrhoeae infections at the cluster level to improve infection management among Indigenous Australian communities with high prevalence of sexually transmissible infections. METHODS: In this cluster-randomised crossover study, we recruited primary health services in Western Australia, Far North Queensland, and South Australia that provide care to Indigenous people in regional or remote locations. The services were eligible if they did 150 or more tests for C trachomatis or N gonorrhoeae infection per year among individuals aged 16-29 years, and if C trachomatis or N gonorrhoeae positivity was 10% or higher. Services were randomly assigned (1:1) by use of a random-number generator, stratified by geographical region, to either standard care conditions with routine laboratory-based sexually transmissible infection testing for 12 months followed by 12 months of intervention with molecular point-of-care testing, or the reverse sequence. The primary outcome was the proportion of people (aged 16-29 years) found to have C trachomatis or N gonorrhoeae who had a positive result at retesting 3 weeks to 3 months after treatment, and a secondary outcome was treatment within 7 days, both in those aged 16-29 years and at the cluster level. We did these analyses using data from all participants who had a positive result at testing, by point-of-care of laboratory testing (ie, the intention-to-treat population). The trial is registered with Australian and New Zealand Clinical Trials Registry (ACTRN12613000808741). FINDINGS: Between June 1, 2013, and Feb 29, 2016, 12 health services were enrolled and randomly assigned to standard care followed by intervention (six) and the reverse sequence (six). After randomisation, one health service that was initially assigned to standard care was excluded because it no longer met the inclusion criteria. 455 individuals tested positive for C trachomatis or N gonorrhoeae infection in the intervention group, and 405 tested positive in the standard care group. In the intervention group, 12 (19%) of 63 individuals retested had a positive test result, compared with nine (13%) of 67 with positive retests in the standard care group (relative ratio [RR] 1·42, 95% CI 0·64-3·13; p=0·405), and 347 (76%) were treated within 7 days in the intervention group, compared with 191 (47%) in the standard care group (RR 1·66, 1·41-1·93; p<0·0001). INTERPRETATION: Retesting rates were too low to draw conclusions on the effect of the intervention on repeat infections. Further research will be needed to determine whether point-of-care tests have an effect on reinfection rates, and the sustainability of using this technology. However, our findings show that time to treatment of C trachomatis or N gonorrhoeae infections in primary care clinics in remote areas in Australia with a high prevalence of sexually transmissible infections could be substantially reduced by the use of molecular point-of-care tests. FUNDING: The National Health and Medical Research Council, Australia.

Molecular test for chlamydia and gonorrhoea used at point of care in remote primary healthcare settings: a diagnostic test evaluation.

OBJECTIVES: A new molecular test for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) (GeneXpert CT/NG) has been demonstrated to be as accurate as conventional nucleic acid amplification tests (NAAT), but performance has not been evaluated in routine primary care, performed at the point of care by clinicians. We aimed to examine its diagnostic performance when used by clinicians in remote community health services in Australia with high prevalences of CT and NG infection. The trial was registered with the Australian and New Zealand Clinical Trials Registry (#12613000808741) METHODS: At 12 health services, training was provided to 99 clinicians in the use of the GeneXpert CT/NG assay who tested specimens from all patients undergoing STI screening. Specimens were also sent in parallel for conventional laboratory-based NAATs and the concordance of results was evaluated. RESULTS: Clinicians conducted 2486 tests: CT concordance was 99.4% (95% CI 99.1 to 99.7) with a positive concordance of 98.6% (95% CI 95.9 to 99.7) and negative concordance of 99.5% (95% CI 99.1 to 99.8); NG concordance was 99.9% (95% CI 99.7 to 100.0) with a positive concordance of 100.0% (95% CI 97.5 to 100.0) and negative concordance of 99.9% (95% CI 99.7 to 100.0). CONCLUSIONS: In this first study reporting routine point-of-care use of GeneXpert CT/NG by primary care clinicians, we found excellent concordance with conventional NAATs. The use of the GeneXpert CT/NG at the point of care could potentially transform management and control of these infections in many endemic settings, including low/middle-income countries.