References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Treatment as Prevention (TasP) means that people with HIV who take effective antiretroviral therapy and maintain an undetectable viral load cannot pass HIV on through sex. This is U=U — Undetectable = Untransmittable. TasP is one of the most powerful tools in the HIV response, protecting both individual health and public health.
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How TasP Works
| Step | Effect |
|---|---|
| Start ART | Suppresses HIV replication |
| Viral load drops | Within weeks to months |
| Reach undetectable | Usually within 3-6 months |
| Sustained undetectable | No sexual transmission possible |
The Evidence
- PARTNER studies: zero transmissions from undetectable partners
- Over 100,000 condomless sex acts studied
- Endorsed globally by WHO, UNAIDS, NHS, BHIVA
Requirements
- Consistent daily ART adherence
- Regular viral load monitoring
- Sustained undetectable viral load
TasP vs PrEP
- TasP: HIV-positive person takes ART — prevents them from transmitting
- PrEP: HIV-negative person takes medication — prevents them from acquiring
- Both work; they complement each other
Read more: U=U explained | PrEP | Treatment adherence
Frequently Asked Questions
Does TasP work for all types of sex?
Yes — vaginal, anal and oral.
Do I still need condoms?
For HIV, no (if undetectable). Condoms still prevent other STIs.
Brief blips don’t usually affect U=U protection.
Related reading
- Injectable HIV Treatment: Everything You Need to Know
- Are HIV Tests Accurate If You're on PrEP, PEP or ART?
- Can Condoms Protect Against HIV?
- CD4/CD8 Ratio: What It Means and Why It Matters
- CD4 Counts Explained: What Your Numbers Mean
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
