Genital Chlamydia trachomatis infections in young adults – a school-based bio-behavioural study in urban areas, Poland, 2012 to 2015

One of the most common sexually transmitted pathogens disproportionately affecting young people is Chlamydia trachomatis (CT). This study aimed to assess prevalence of CT among sexually active students (aged 18–19 years) in their final years of high school education in Warsaw and Krakow. Methods: The sample was selected from 61 clusters, each cluster representing one school. We described city, sex, type of school and their association with CT prevalence. To account for non-responders we applied inverse probability weighting. Results: Our study population consisted of 3,136 young adults eligible for CT screening, of whom 2,326 reported having had sexual intercourse within past 12 months. Of the 950 students who agreed to be tested, 39 were infected with CT. Weighted prevalence of CT was 3.9% (95% confidence interval (CI): 2.7–5.1); however, prevalence in the students in Warsaw (6.6%; 95% CI: 3.5–12.4) was six times higher (prevalence ratio (PR) = 5.9; 95% CI: 2.0–17.3) than in Krakow (1.1%; 95% CI: 0.5–2.6). In both settings, female students attending vocational-technical schools were most affected; the prevalence in this group was more than five times higher (PR = 5.2; 95% CI: 1.7–15.6) compared with female peers in high schools and more than three times higher (PR = 3.3; 95% CI: 1.0–10.7) compared with male peers attending vocational-technical schools. Conclusion: Our study suggested prevalence of CT infection among young people in Poland comparable with the European average, supporting implementation of a CT control programme as recommended in international guidelines.