Sexual infections and teenage pregnancies disproportionately affect people living in poverty and social exclusion. In 2004, the government white paper “Choosing health”1 identified sexual health as a priority area for improvement and service development. The paper followed the publication of the National Strategy for Sexual Health and HIV,2 which aims to provide “better prevention, better services, and better sexual health.” The strategy described the implementation of a broad National Chlamydia Screening Programme (NCSP) in accordance with the National Health Service plan, which included “a commitment to improving the prevention of ill health and providing screening programmes where they are appropriate.” In this week's BMJ, an analysis by Low shows how acceptance of the effectiveness of chlamydial screening programmes in Sweden and the United States supported the funding of the National Chlamydia Screening Programme before the balance of benefits and harms was thoroughly understood.3

Chlamydia is the most common sexually transmitted disease in England. Its prevalence has increased steadily since the mid-1990s, and rose by 300% from 1995 to 2004. The main burden of infection affects women aged 16-19 and men aged 20-24 years. Although often asymptomatic, associated problems such as pelvic inflammatory disease, infertility, ectopic pregnancy, epididymo-orchitis, ophthalmic complications, and neonatal complications are well described. As with most sexually transmitted infections, Chlamydia trachomatis may be a cofactor for HIV transmission.

Chlamydia is the only sexually transmitted infection for which population screening …