Capturing sexual contact patterns in modelling the spread of sexually transmitted infections: Evidence using Natsal-3

Transmission matrices used in epidemiologic modelling

Mixing matrices are included in infectious disease models to reflect transmission opportunities between population strata. These matrices were originally constructed on the basis of theoretical considerations and most of the early work in this area originates from research on sexually transferred diseases in the 80s, in response to AIDS. Later work in the 90s populated these matrices on the basis of survey data gathered to capture transmission risks for respiratory diseases. We provide an overview of developments in the construction of matrices for capturing transmission opportunities in populations. Such transmission matrices are useful for epidemiologic modelling to capture within and between stratum transmission and can be informed from theoretical mixing assumptions, informed by empirical evidence gathered through investigation as well as generated on the basis of data. Links to summary measures and threshold conditions are also provided.

Clinical and Public Health Considerations for HPV Vaccination in Midadulthood: A Narrative Review

Human papillomavirus (HPV) is an important cause of anogenital and oropharyngeal cancers, anogenital warts, and recurrent respiratory papillomatosis. Beginning in 2019, US guidelines recommended shared clinical decision-making (SCDM) for HPV vaccination among midadults (27-45 years). We conducted a narrative review of existing literature on HPV vaccination in midadults. The available evidence demonstrates that HPV vaccination in midadults is safe, efficacious, and likely to benefit both HPV-naïve midadults and those with previous infections. However, gaps in knowledge related to HPV vaccination have been identified among clinicians and midadult patients. Universal midadult HPV vaccination in the United States could avert 20 934-37 856 cancer cases over 100 years, costing $141 000-$1 471 000 per quality-adjusted life-year gained. Wide variation in these estimates reflects uncertainties in sexual behavior, HPV natural history, and naturally acquired immunity. Greater awareness among clinicians and midadult patients and broad implementation of SCDM may accelerate progress toward eliminating HPV-associated cancers and other diseases.

Health Impact and Cost-Effectiveness of Implementing Gender-Neutral Vaccination With the 9-Valent Human Papillomavirus Vaccine in Belgium

Background: Routine human papillomavirus (HPV) immunization in Belgium is currently regionally managed, with school-aged girls receiving the 9-valent HPV (9vHPV) vaccine in Flanders and Wallonia-Brussels with a national catch-up program for females only. This study will assess whether expanding these programs to gender-neutral vaccination (GNV) with the 9vHPV vaccine is a cost-effective strategy in Belgium. Methods: A validated HPV-type transmission dynamic model estimated the potential health and economic impact of regional vaccination programs, comparing GNV versus female-only vaccination (FOV) with the 9vHPV vaccine in individuals aged 11-12 years in Flanders, GNV with the 9vHPV vaccine versus FOV with the 2-valent HPV (2vHPV) vaccine in individuals aged 12-13 years in Wallonia-Brussels, and national catch-up GNV versus FOV with the 9vHPV vaccine for those aged 12-18 years. Vaccination coverage rates of 90, 50, and 50% in both males and females were used in the base cases for the three programs, respectively, and sensitivity analyses were conducted. All costs are from the third-party payer perspective, and outcome measures were reported over a 100-year time horizon. Results: GNV with the 9vHPV vaccine was projected to decrease the cumulative incidence of HPV 6/11/16/18/31/33/45/52/58-related diseases relative to FOV in both Flanders and Wallonia-Brussels. Further reductions were also projected for catch-up GNV with the 9vHPV vaccine, including reductions of 6.8% (2,256 cases) for cervical cancer, 7.1% (386 cases) and 18.8% (2,784 cases) for head and neck cancer in females and males, respectively, and 30.3% (82,103 cases) and 44.6% (102,936 cases) for genital warts in females and males, respectively. As a result, a GNV strategy would lead to reductions in HPV-related deaths. Both regional and national catch-up GNV strategies were projected to reduce cumulative HPV-related disease costs and were estimated to be cost-effective compared with FOV with incremental cost-effectiveness ratios of €8,062, €4,179, and €6,127 per quality-adjusted life-years in the three programs, respectively. Sensitivity analyses were consistent with the base cases. Conclusions: A GNV strategy with the 9vHPV vaccine can reduce the burden of HPV-related disease and is cost-effective compared with FOV for both regional vaccination programs and the national catch-up program in Belgium.

Contact Mixing Patterns and Population Movement among Migrant Workers in an Urban Setting in Thailand

Data relating to contact mixing patterns among humans are essential for the accurate modeling of infectious disease transmission dynamics. Here, we describe contact mixing patterns among migrant workers in urban settings in Thailand, based on a survey of 369 migrant workers of three nationalities. Respondents recorded their demographic data, including age, sex, nationality, workplace, income, and education. Each respondent chose a single day to record their contacts; this resulted in a total of more than 8300 contacts. The characteristics of contacts were recorded, including their age, sex, nationality, location of contact, and occurrence of physical contact. More than 75% of all contacts occurred among migrants aged 15 to 39 years. The contacts were highly clustered in this age group among migrant workers of all three nationalities. There were far fewer contacts between migrant workers with younger and older age groups. The pattern varied slightly among different nationalities, which was mostly dependent upon the types of jobs taken. Half of migrant workers always returned to their home country at most once a year and on a seasonal basis. The present study has helped us gain a better understanding of contact mixing patterns among migrant workers in urban settings. This information is useful both when simulating disease epidemics and for guiding optimal disease control strategies among this vulnerable section of the population.

Modelling microbial infection to address global health challenges

The continued growth of the world’s population and increased interconnectivity heighten the risk that infectious diseases pose for human health worldwide. Epidemiological modelling is a tool that can be used to mitigate this risk by predicting disease spread or quantifying the impact of different intervention strategies on disease transmission dynamics. We illustrate how four decades of methodological advances and improved data quality have facilitated the contribution of modelling to address global health challenges, exemplified by models for the HIV crisis, emerging pathogens and pandemic preparedness. Throughout, we discuss the importance of designing a model that is appropriate to the research question and the available data. We highlight pitfalls that can arise in model development, validation and interpretation. Close collaboration between empiricists and modellers continues to improve the accuracy of predictions and the optimization of models for public health decision-making.

Correlations between stochastic endemic infection in multiple interacting subpopulations

Heterogeneity plays an important role in the emergence, persistence and control of infectious diseases. Metapopulation models are often used to describe spatial heterogeneity, and the transition from random- to heterogeneous-mixing is made by incorporating the interaction, or coupling, within and between subpopulations. However, such couplings are difficult to measure explicitly; instead, their action through the correlations between subpopulations is often all that can be observed. We use moment-closure methods to investigate how the coupling and resulting correlation are related, considering systems of multiple identical interacting populations on highly symmetric complex networks: the complete network, the k-regular tree network, and the star network. We show that the correlation between the prevalence of infection takes a relatively simple form and can be written in terms of the coupling, network parameters and epidemiological parameters only. These results provide insight into the effect of metapopulation network structure on endemic disease dynamics, and suggest that detailed case-reporting data alone may be sufficient to infer the strength of between population interaction and hence lead to more accurate mathematical descriptions of infectious disease behaviour.

Infection as a potential cofactor in the genetic-epigenetic pathophysiology of endometriosis: a systematic review

BACKGROUND

The genetic-epigenetic theory postulates that endometriosis is triggered by a cumulative set of genetic-epigenetic (GE) incidents. Pelvic and upper genital tract infection might induce GE incidents and thus play a role in the pathogenesis of endometriosis. Thus, this article aims to review the association of endometriosis with upper genital tract and pelvic infections.

METHODS

Pubmed, Scopus and Google Scholar were searched for 'endometriosis AND (infection OR PID OR bacteria OR viruses OR microbiome OR microbiota)', for 'reproductive microbiome' and for 'reproductive microbiome AND endometriosis', respectively. All 384 articles, the first 120 'best match' articles in PubMed for 'reproductive microbiome' and the first 160 hits in Google Scholar for 'reproductive microbiome AND endomytriosis' were hand searched for data describing an association between endometriosis and bacterial, viral or other infections. All 31 articles found were included in this manuscript.

RESULTS

Women with endometriosis have a significantly increased risk of lower genital tract infection, chronic endometritis, severe PID and surgical site infections after hysterectomy. They have more colony forming units of Gardnerella, Streptococcus, Enterococci and Escherichia coli in the endometrium. In the cervix Atopobium is absent, but Gardnerella, Streptococcus, Escherichia, Shigella, and Ureoplasma are increased. They have higher concentrations of Escherichia Coli and higher concentrations of bacterial endotoxins in menstrual blood. A Shigella/Escherichia dominant stool microbiome is more frequent. The peritoneal fluid of women with endometriosis contains higher concentrations of bacterial endotoxins and an increased incidence of mollicutes and of HPV viruses. Endometriosis lesions have a specific bacterial colonisation with more frequently mollicutes (54%) and both high and medium-risk HPV infections (11%). They contain DNA with 96% homology with Shigella. In mice transplanted endometrium changes the gut microbiome while the gut microbiome influences the growth of these endometriosis lesions.

CONCLUSIONS

Endometriosis is associated with more upper genital tract and peritoneal infections. These infections might be co-factors causing GE incidents and influencing endometriosis growth.

Assessing the cost-effectiveness of HPV vaccination strategies for adolescent girls and boys in the UK

BACKGROUND

Human papillomavirus (HPV) is the most widespread sexually transmitted infection worldwide. It causes several health consequences, in particular accounting for the majority of cervical cancer cases in women. In the United Kingdom, a vaccination campaign targeting 12-year-old girls started in 2008; this campaign has been successful, with high uptake and reduced HPV prevalence observed in vaccinated cohorts. Recently, attention has focused on vaccinating both sexes, due to HPV-related diseases in males (particularly for high-risk men who have sex with men) and an equity argument over equalising levels of protection.

METHODS

We constructed an epidemiological model for HPV transmission in the UK, accounting for nine of the most common HPV strains. We complemented this with an economic model to determine the likely health outcomes (healthcare costs and quality-adjusted life years) for individuals from the epidemiological model. We then tested vaccination with the three HPV vaccines currently available, vaccinating either girls alone or both sexes. For each strategy we calculated the threshold price per vaccine dose, i.e. the maximum amount paid for the added health benefits of vaccination to be worth the cost of each vaccine dose. We calculated results at 3.5% discounting, and also 1.5%, to consider the long-term health effects of HPV infection.

RESULTS

At 3.5% discounting, continuing to vaccinate girls remains highly cost-effective compared to halting vaccination, with threshold dose prices of £56-£108. Vaccination of girls and boys is less cost-effective (£25-£53). Compared to vaccinating girls only, adding boys to the programme is not cost-effective, with negative threshold prices (-£6 to -£3) due to the costs of administration. All threshold prices increase when using 1.5% discounting, and adding boys becomes cost-effective (£36-£47). These results are contingent on the UK's high vaccine uptake; for lower uptake rates, adding boys (at the same uptake rate) becomes more cost effective.

CONCLUSIONS

Vaccinating girls is extremely cost-effective compared with no vaccination, vaccinating both sexes is less so. Adding boys to an already successful girls-only programme has a low cost-effectiveness, as males have high protection through herd immunity. If future health effects are weighted more heavily, threshold prices increase and vaccination becomes cost-effective.