Prevalence of Chlamydia trachomatis in the general population in Germany – a triangulation of data from two population-based health surveys and a laboratory sentinel system
Authors: Gassowski Martyna , Poethko-Müller Christina , Schlaud Martin , Sailer Andrea , Dehmel Kerstin , Bremer Viviane , Dudareva Sandra , Jansen Klaus ,   Chlamydia trachomatis laboratory sentinel team, Baier Michael , Straube Eberhard , Baillot Armin , Bartsch Patricia , Brüning Thomas , Cremer Josef , Dallügge-Tamm Helga , Gröning Arndt , Eicke Stephan , Emrich Dagmar , Fritsche Gundula , Gjavotchanoff Rosi , Gohl Peter , Götzrath Matthias , Meye Axel , Ehrhard Ingrid , Köpke Beate , Henrich Birgit , Kastilan Caroline , Lehmann Susanne , Märzacker Anneliese , Miller Bernhard , Mohrmann Gerrit , Pache Christian , Pfüller Roland , Tiemann Carsten , Wisplinghoff Hilmar , Müller Thomas , Aepinus Christian 
Published: June 2022

Abstract
Background
Chlamydia trachomatis (chlamydia) is a common, frequently asymptomatic, sexually transmitted infection. It can result in severe sequelae, such as ectopic pregnancy and infertility. In Germany, chlamydia is not notifiable. An opportunistic screening program for women < 25 years was introduced in 2008. The aim of this research was to triangulate different data sources to describe the epidemiological situation of chlamydia in Germany and to investigate whether the current target group of the chlamydia screening program aligns with these findings.

Methods
Urine specimens from participants from population-based health examination surveys of children (2014–17) and adults (2008–11) were tested for chlamydia, using nucleic acid amplification testing. These data were used to generate weighted chlamydia prevalence estimates by age group and sex. Data from a nationwide chlamydia laboratory sentinel system (2014–16) were used to calculate the positive proportion among individuals tested for chlamydia by age, sex and test reason.

Results
Using data from the population-based surveys, we found a chlamydia prevalence estimate of 2.8% (95% confidence interval (CI) 1.0–7.5%) among all 15- to 17-year-old girls and of 9.6% (95% CI 0.0–23) among those reporting to be sexually active. In adult women, we found the highest prevalence among 18- to 24-year-olds (all: 2.3%; 95% CI 1.0–5.3%; sexually active: 3.1%; 95% CI 1.3–7.0%). In adult men, we found the highest prevalence among 25- to 29-year-olds (all: 3.5%; 95% CI 1.6–7.7%; sexually active: 3.3%; 95% CI 1.3–7.8%). Data from the chlamydia laboratory sentinel showed the highest positive proportion among those opportunistically screened in 19-year-old women (6.1%; 95%- CI 5.9–6.4%), among those screened due to pregnancy in 15-year-old girls (10%; 95% CI 8.5–12%), and among those tested due to symptoms or a positive partner in 19-year-old women (10%; 95% CI 9.8–11%) and 19-year-old men (24%; 95% CI 22–26%).

Conclusions
Chlamydia seems to mainly affect adolescents and young adults in Germany, with similar overall prevalence in men and women, but with slightly different age distributions. Women at highest risk of chlamydia are covered by the current screening program but given the on-going discussions in high-income countries on cost-effectiveness and benefit-to-harm ratio of these programs, the program-aim needs reconsideration.