Youngsters will be offered the chance to do a chlamydia test at home.
The sexual health team at Central Essex Community Services (CECS) will be writing to all 44,000 16 to 24-year-olds in mid Essex from February 13.
Kez Spelman, CECS's sexual health nurse consultant, said: “Chlamydia is still the most common sexually transmitted infection in the UK.
“In many cases there are no symptoms so people often don’t know that they have it.
“I would urge people to take up this offer, the test is quick and easy to do and the treatment simple and effective.”
Chlamydia is passed from one person to another through unprotected sex.
Left untreated, it can lead to long-term health problems such as pelvic inflammatory disease and infertility.
To request a test you can text or email your name, date of birth and address to 07900 248 718 or email@example.com You can telephone 0300 003 1212, attend your local clinic or go to www.cecs.org.uk/chlamydia-home-testing-kit