Chlamydia is the most commonly diagnosed sexually transmitted infection. It causes avoidable sexual and reproductive ill-health, including symptomatic acute infections and complications such as pelvic inflammatory disease (PID), ectopic pregnancy and infertility.

The rates of chlamydia are substantially higher in young adults than any other age group. By diagnosing and treating asymptomatic infections, chlamydia screening can reduce the duration of infection. This will subsequently reduce an individual’s chance of developing complications, the time when someone is at risk of passing the infection on and ultimately the spread of chlamydia in the population.


Chlamydia screening is recommended for all sexually active people under 25 and on partner change. The Public Health Outcomes Framework includes an indicator on the chlamydia detection rate amongst under 25 year olds. This is not a measure of morbidity, but instead monitors local chlamydia control activities and the delivery of accessible, high volume chlamydia screening. Public Health England recommends that local authorities should be working towards achieving a detection rate of at least 2,300 per 100,000 population (aged 15 to 24).

Facts and figures

Read our Chlamydia facts and figures (PDF document).