By Nick Triggle
Health reporter, BBC News
People with chlamydia may not have any symptoms
The NHS has missed its target for chlamydia testing, but has still shown good progress in the past year.
The screening programme in England was supposed to reach 17% of the 15 to 24 age group, but 15.9% were checked in 2008-9, official figures showed.
However, the figure represents a significant improvement on the previous year when fewer than 5% were tested.
Funding problems and engaging young people have been blamed for the slow roll out.
Chlamydia is the most common sexual infection with 120,000 new cases diagnosed last year, with young people accounting for two thirds of them.
It is known as the "silent infection", as it often shows no symptoms, but if left untreated can cause infertility.
The screening programme was introduced in several pilot areas in 2002 to address the risks from the rising number of cases.
Screening is done via urine tests, mainly in contraceptive clinics, GP surgeries or through outreach work in bars, clubs and colleges, as it has been designed to get to people not using sexual health services.
Over the last few years, testing has been gradually rolled out across the country, with the government pumping £70m into the NHS to get it fully up and running by 2007-8.
During that year just three of the 152 NHS trusts responsible for the programme hit the target, but that has now increased to half the total number with 1m tests carried out overall.
Paul Ward, deputy chief executive at Terrence Higgins Trust, which has helped provide screening in some areas, said: "The past year has seen more young people screened for chlamydia than ever before, however, more still needs to be done if we're to see the number of new infections decline.
"Trusts must learn from successful schemes by encouraging a joined up approach from GPs, sexual health clinics and outreach programmes. "