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.
HIV can be transmitted through vaginal sex, though the per-act risk is lower than for anal sex. The receptive partner (usually the woman) faces a higher risk than the insertive partner (usually the man). Many factors influence the actual risk, and several highly effective prevention methods are available.
Here’s what the evidence shows.
Order a discreet home HIV test
Risk Levels
| Activity | Estimated Risk per 10,000 Exposures* |
|---|---|
| Receptive vaginal sex (woman) | Around 8 |
| Insertive vaginal sex (man) | Around 4 |
| Receptive anal sex | Around 138 (for comparison) |
*Assumes the source partner is HIV-positive with a detectable viral load and no condom or PrEP is used.
Factors That Increase Risk
- High viral load — especially during acute (recent) infection
- Other STIs — particularly ulcerative infections like herpes and syphilis
- Menstruation — blood increases viral exposure
- Vaginal inflammation or BV
- Cervical ectopy — more common in younger women
- Lack of circumcision in the male partner (slightly higher risk)
Factors That Eliminate or Reduce Risk
- U=U — if the HIV-positive partner is undetectable, transmission risk is zero
- PrEP — reduces risk by over 99% when taken daily for 21+ days (vaginal sex needs longer to achieve full protection than anal)
- Condoms — very effective when used correctly
- Male circumcision — reduces female-to-male risk by about 60%
PrEP and Vaginal Sex
Daily PrEP takes longer to reach protective levels in vaginal tissue than in rectal tissue — about 21 days of daily use for full protection, compared to about 7 days for anal sex. Event-based (on-demand) PrEP is not recommended for vaginal sex — daily dosing is the only validated approach.
What to Do After a Possible Exposure
- Within 72 hours: Contact a sexual health clinic or A&E about PEP
- At 4 weeks: Get a 4th-generation HIV test
- At 3 months: Confirmatory test if the first was negative
- Consider PrEP if you’re at ongoing risk
Read more: Estimating HIV risk | Condoms and HIV | PrEP
Frequently Asked Questions
Can I get HIV from one act of vaginal sex?
Yes, though the per-act risk is low. It depends heavily on viral load, protection used and other factors.
Is the woman or man more at risk?
The receptive partner (usually the woman) faces roughly double the per-act risk of the insertive partner.
Does PrEP work for vaginal sex?
Yes, but it must be taken daily for at least 21 days before relying on it for vaginal sex protection. Event-based dosing is not validated for vaginal sex.
Related reading
- Can You Test for STIs While on Your Period?
- Common STI Symptoms in Women
- Does a Vaginal Yeast Infection Smell?
- How Different STIs Affect Vaginal Discharge
- Incubation Periods for STIs: When Symptoms Appear
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.
