Biology subjects

Althaus, C. L.

Publications and source records attributed to Althaus, C. L..

5 recordsLinked to original sources

bioRxiv2018

Discrepancies between observed data and predictions from mathematical modelling of the impact of screening interventions on Chlamydia trachomatis prevalence

Mathematical modelling studies of C. trachomatis transmission predict that interventions to screen and treat chlamydia infection will reduce prevalence to a greater degree than that observed in empirical population-based studies. We investigated two factors that might explain this discrepancy: partial immunity after natural infection clearance and differential screening coverage according to infection risk. We used four variants of a compartmental model for heterosexual C. trachomatis transmission, parameterized using data from England about sexual behaviour and C. trachomatis testing, diagnosis and prevalence, and Markov Chain Monte Carlo methods for statistical inference. A model in which partial immunity follows natural infection clearance and the proportion of tests done in chlamydia-infected people decreases over time fitted the data best. The model predicts that partial immunity reduced susceptibility to reinfection by 72% (95% Bayesian credible interval 57-86%). The estimated screening rate was 4.6 (2.6-6.5) times higher for infected than for uninfected women in 2000; this decreased to 2.1 (1.4-2.9) in 2011. Other factors not included in the model could have further reduced the expected impact of screening. Future mathematical modelling studies investigating the effects of screening interventions on C. trachomatis transmission should incorporate host immunity and changes over time in the targeting of screening.

epidemiology↗

bioRxiv2018

De novo mutations drive the spread of macrolide resistant Mycoplasma genitalium: mathematical modelling study

BackgroundThe rapid spread of azithromycin resistance in sexually transmitted Mycoplasma genitalium infections is a growing concern. It is not yet clear to what degree macrolide resistance in M. genitalium results from the emergence of de novo mutations or the transmission of resistant strains.\n\nMethodsWe analyzed epidemiological data and developed a compartmental model to investigate the contribution of de novo macrolide resistance mutations to the spread of antimicrobial-resistant M. genitalium. We fitted the model to data from France, Denmark and Sweden and estimated treatment rates of infected individuals and the time point of azithromycin introduction.\n\nResultsWe found a high probability of de novo resistance (12%, 95% CI 8-17%), which is responsible for the observed rapid spread of antimicrobial resistant M. genitalium. The estimated per capita treatment rate in France was lower than in Denmark and Sweden but confidence intervals for the three estimates overlap. The estimated dates of introduction of azithromycin in each country are consistent with published reports.\n\nConclusionsSince de novo resistance is the main driver of macrolide resistance in M. genitalium, blind treatment of urethritis with azithromycin is not recommended. Clinical management strategies for M. genitalium should limit the unnecessary use of macrolides.

microbiology↗

bioRxiv2017

Exploring variation in human papillomavirus vaccination uptake: multi-level spatial analysis

BackgroundUnderstanding the factors that influence human papillomavirus (HPV) vaccination uptake is critically important to design effective vaccination programmes. In Switzerland, completed HPV vaccination by age 16 years among women ranges from 30 to 79% across 26 cantons (states). Our objective was to identify factors that are associated with the spatial variation in HPV vaccination uptake.\n\nMethods and findingsWe used data from the Swiss National Vaccination Coverage Survey 2009-2016 on HPV vaccination status ([≥]1 dose) of 14-17 year old girls, their municipality of residence and their nationality for 21 of 26 cantons (N=8,965). We examined covariates at municipality level: language, degree of urbanisation, socio-economic position, religious denomination, results of a vote about vaccination laws; and, at cantonal level, availability of school-based vaccination and survey period. We used a series of conditional auto regressive (CAR) models to assess the effects of covariates while accounting for variability between cantons and municipal-level spatial autocorrelation. In the best-fit model, school-based vaccination (adjusted odds ratio, OR: 2.51, 95% credible interval, CI: 1.77-3.56) was associated with increased uptake, while lower acceptance of vaccination laws was associated with lower HPV vaccination uptake (OR 0.61, 95% CI: 0.50-0.73). Overall, the covariates explained 88% of the municipal-level variation in uptake.\n\nConclusionsIn Switzerland, cantons play a prominent role in the variation in HPV vaccination uptake, especially through the provision of school-based vaccination delivery. HPV vaccination uptake is also strongly associated with inhabitants attitudes towards vaccination. To increase uptake, efforts should be made both to mitigate vaccination scepticism and to encourage school-based vaccination.

epidemiology↗

bioRxiv2017

Antibiotic Resistance Detection Is Essential For Gonorrhoea Point-Of-Care Testing: A Mathematical Modelling Study

Antibiotic resistance is threatening to make gonorrhoea untreatable. Point-of-care (POC) tests that detect resistance promise individually tailored treatment, but might lead to more treatment and higher levels of resistance. We investigate the impact of POC tests on antibiotic-resistant gonorrhoea. We used data about the prevalence and incidence of gonorrhoea in men who have sex with men (MSM) and heterosexual men and women (HMW) to calibrate a mathematical gonorrhoea transmission model. With this model, we simulated four clinical pathways for the diagnosis and treatment of gonorrhoea: POC test with (POC + R) and without (POC - R) resistance detection, culture, and nucleic acid amplification tests (NAATs). We calculated the proportion of resistant infections, cases averted after 5 years, and compared how fast resistant infections spread in the populations. The proportion of resistant infections after 30 years is lowest for POC + R (median MSM: 0.18%, HMW: 0.12%), and increases for culture (MSM: 1.19%, HWM: 0.13%), NAAT (MSM: 100%, HMW: 99.27%), and POC - R (MSM: 100%, HMW: 99.73%). NAAT leads to 36 366 (median MSM) and 1 228 (median HMW) observed cases after 5 years. When compared with NAAT, POC + R results in most cases averted after 5 years (median MSM: 3 353, HMW: 118 per 100 000 persons). POC tests that detect resistance with intermediate sensitivity slow down resistance spread more than NAAT. POC tests with very high sensitivity for the detection of resistance are needed to slow down resistance spread more than using culture. POC with high sensitivity to detect antibiotic resistance can keep gonorrhoea treatable longer than culture or NAAT. POC tests without reliable resistance detection should not be introduced because they can accelerate the spread of antibiotic-resistant gonorrhoea.

epidemiology↗

bioRxiv2017

Modeling the consequences of regional heterogeneity in human papillomavirus (HPV) vaccination uptake on transmission in Switzerland

BackgroundCompleted human papillomavirus (HPV) vaccination by age 16 years among women in Switzerland ranges from 17 to 75% across 26 cantons. The consequences of regional heterogeneity in vaccination coverage on transmission and prevalence of HPV-16 are unclear.\n\nMethodsWe developed a deterministic, population-based model that describes HPV-16 transmission among young adults within and between the 26 cantons of Switzerland. We parameterized the model using sexual behavior data from Switzerland and data from the Swiss National Vaccination Coverage Survey. First, we investigated the general consequences of heterogeneity in vaccination uptake between two sub-populations. We then compared the predicted prevalence of HPV-16 after the introduction of heterogeneous HPV vaccination uptake in all of Switzerland with homogeneous vaccination at an uptake that is identical to the national average (52%).\n\nResultsHPV-16 prevalence in women is 3.34% when vaccination is introduced and begins to diverge across cantons, ranging from 0.14 to 1.09% after 15 years of vaccination. After the same time period, overall prevalence of HPV-16 in Switzerland is only marginally higher (0.55 %) with heterogeneous vaccination uptake than with homogeneous uptake (0.49%). Assuming inter-cantonal sexual mixing, cantons with low vaccination uptake benefit from a reduction in prevalence at the expense of cantons with high vaccination uptake.\n\nConclusionsRegional variations in uptake diminish the overall effect of vaccination on HPV-16 prevalence in Switzerland, although the effect size is small. Cantonal efforts towards HPV-prevalence reduction by increasing vaccination uptake are impaired by cantons with low vaccination uptake. Harmonization of cantonal vaccination programs would reduce inter-cantonal differences in HPV-16 prevalence.

epidemiology↗