I have had Chlamydia. Am I now immune?

No. UK guidelines say Chlamydia gives only limited immunity, so you can catch it again after it’s been treated. People who have had Chlamydia are actually more likely to test positive again than people who haven’t, often because of a partner who wasn’t treated or a new partner.

There’s no vaccine for Chlamydia yet. The World Health Organization says vaccine candidates are still in early clinical development.

Having Chlamydia once doesn’t stop you getting it again.

Repeat infections are common, especially in young people:

• about 10% to 15% of young adults diagnosed with Chlamydia test positive again at their next test
• people who have tested positive are 2 to 3 times more likely to test positive at their next test than people who tested negative
• in England in 2025, there were 151,163 Chlamydia diagnoses, and about half were in people aged 15 to 24

If you’re young and sexually active, it’s worth planning your next test now. Read more in “Why is Chlamydia known as a silent STI?”

The most common reasons are:

• a partner who wasn’t treated: if you have sex with them again, the infection can pass straight back to you
• sex before treatment had finished: for you or your partner
• a new or existing partner who has Chlamydia: especially if you don’t use condoms
• shared sex toys: Chlamydia can spread on toys that aren’t washed and covered with a new condom

Rarely, in under 5% of cases, the antibiotic doesn’t fully clear the first infection.

Most repeat infections are new infections, not the old one coming back.

Not usually. UK guidelines recommend doxycycline, an antibiotic taken twice a day for 7 days, which cured everyone in a trial the guidelines cite. If you’re pregnant, you’ll be given a different antibiotic that’s safe in pregnancy. Treatment works very well, as long as you take the full course.

A positive test soon after treatment doesn’t always mean the infection is back. Genetic material from dead bacteria can still show up on a test for 3 to 5 weeks. That’s why a test to check treatment has worked isn’t usually needed. When it is, for example if you’re pregnant, missed doses or still have symptoms, it’s done at least 3 weeks after you finish treatment.

Take every tablet, and don’t test again too soon. Read more in “Can an STI come back after treatment?”

After a positive result:

• take all your antibiotics, even if you feel better
• don’t have sex, including oral sex, until you and your partner have finished treatment and your symptoms have gone. If you’re given azithromycin instead of doxycycline, wait 7 days after taking it
• make sure your partners are tested and treated before you have sex with them again
• use condoms with new partners, and with anyone whose STI status you don’t know

Partners from the last 6 months should usually be told. For men with symptoms from the penis, it’s partners since the symptoms started and in the 4 weeks before.

If your partner isn’t treated, you can catch it straight back.

UK guidelines recommend testing again:

• about 3 months after treatment, if you’re under 25
• at any age, if your symptoms come back or you have sex with a new partner
• 4 weeks after treatment, if you’re pregnant, to check it has worked

After sex with a new partner, you can test for Chlamydia from 2 weeks.

A repeat test at about 3 months finds infections you might not notice. Read more in “How to test for Chlamydia: which sample you need and when”

Each Chlamydia infection can cause harm if it isn’t treated, and UK screening experts say repeat infections raise the risk:

• in women: untreated Chlamydia leads to pelvic inflammatory disease in about 1 in 6, which can cause infertility, ectopic pregnancy and long-term pelvic pain. The risk is higher if you get Chlamydia again and again
• in men: it can cause a painful infection in the testicles, which in rare cases can affect fertility
• in anyone: it can trigger reactive arthritis, with painful, swollen joints

Treating each infection quickly protects your long-term health. Read more in “Which STIs can cause infertility?”

Better2Know offers:

• Chlamydia home test: a urine test from 14 days after sex, with results in 2 days.
• Chlamydia and Gonorrhoea (Urine): tests one urine sample for both infections, from 14 days after sex, with results in 2 days. You can book it at one of our clinics or have a nurse visit you.
• Chlamydia and Gonorrhoea (Vaginal Swab): for women, a swab you take yourself, which is the sample UK guidelines recommend, from 14 days after sex, with results in 2 days. You can also order a home test kit.
• Peace of Mind: adds a blood test for Syphilis, from 14 days after sex, with results in 2 days.

If you have symptoms, you don’t need to wait to get tested, but if you test within 2 weeks of sex, you may need a repeat test. A Syphilis test in the first 3 months after sex can miss the infection, so you may need a repeat test. Not sure which test you need? Our Patient Care Team is available 24/7 on 020 7099 0955.

Can I catch Chlamydia from the same partner again?

Yes. If your partner isn’t treated, or you have sex before you’ve both finished treatment, the infection can pass back to you.

Is there a vaccine for Chlamydia?

Not yet. Vaccines are being developed, but they’re still in early trials.

Will a test straight after treatment show whether it’s gone?

Not reliably. Genetic material from dead bacteria can be detected for 3 to 5 weeks, so a test too soon can be positive even when the infection has cleared.

Having Chlamydia once doesn’t make you immune, and repeat infections are common, especially in young people. Finish your treatment, make sure your partners are treated too, use condoms with new partners, and if you’re under 25, test again about 3 months later.

Order a Chlamydia home test or book a Chlamydia and Gonorrhoea test at a clinic near you. Our Patient Care Team is available 24/7 on 020 7099 0955.

Not in the UK? Choose your country from the selector at the top of the page for local tests and prices.

This article originally appeared on 10 February 2023 and was last updated on 1 October 2026.

This article is general information and not a substitute for personal medical advice.

Sources

1. NHS, Chlamydia, reviewed 24 October 2024. https://www.nhs.uk/conditions/chlamydia/
2. NHS, Pelvic inflammatory disease, reviewed 17 December 2025. https://www.nhs.uk/conditions/pelvic-inflammatory-disease-pid/
3. British Association for Sexual Health and HIV, UK national guideline for the management of infection with Chlamydia trachomatis, 2026. https://www.bashh.org/_userfiles/pages/files/national_guideline_for_the_management_of_infection_chlamydia_trachomatis_2026.pdf
4. British Association for Sexual Health and HIV, A guide to Chlamydia, July 2026. https://www.bashh.org/_userfiles/pages/files/chlamydia_pil_mobilepdf_02.pdf
5. British Association for Sexual Health and HIV, Summary guidance on testing for sexually transmitted infections, 2023. https://www.bashh.org/_userfiles/pages/files/resources/bashh_summary_guidance_on_stis_testing_2023.pdf
6. British Association for Sexual Health and HIV, UK guidelines for the management of syphilis, 2024. https://bashh.org/_userfiles/pages/files/syphilis_2024.pdf
7. UK Health Security Agency, NCSP: programme overview, 24 June 2021. https://www.gov.uk/government/publications/ncsp-programme-overview/ncsp-programme-overview
8. UK Health Security Agency, NCSP: patient information leaflet (text version), 1 November 2024. https://www.gov.uk/government/publications/ncsp-patient-information-leaflets/ncsp-patient-information-leaflet-text-version
9. National Chlamydia Screening Programme, Re-testing of positive chlamydia cases: evidence summary, August 2013. https://assets.publishing.service.gov.uk/media/5a80ec43ed915d74e6231360/NCSP_evidence_summary_Re-testing_of_Positive_Chlamydia_Cases__August_2013_FINAL.pdf
10. UK Health Security Agency, Sexually transmitted infections and screening for chlamydia in England: 2025 report, 2 June 2026. https://www.gov.uk/government/statistics/sexually-transmitted-infections-stis-annual-data-tables/sexually-transmitted-infections-and-screening-for-chlamydia-in-england-2025-report
11. World Health Organization, Chlamydia, 21 November 2025. https://www.who.int/news-room/fact-sheets/detail/chlamydia
12. World Health Organization, Sexually transmitted infections (STIs), 10 September 2025. https://www.who.int/news-room/fact-sheets/detail/sexually-transmitted-infections-(stis)