Prevention

Preventing STIs and practicing safer sex

Most STI risk can be reduced with consistent prevention strategies. This guide covers barrier methods, medications, vaccines, and habits that protect you and your partners — without judgment.

Core prevention strategies

No single method is 100% effective against every STI. Combining approaches gives the strongest protection.

Barrier methods

Condoms (external and internal) and dental dams reduce contact with semen, vaginal fluids, blood, and some skin-to-skin exposure. They are among the most accessible prevention tools.

Use a new condom for every act of vaginal, anal, or oral sex
Check the expiration date and open carefully (no teeth or sharp nails)
Use water-based or silicone lubricant with latex — oil-based products can weaken latex
Dental dams or cut-open condoms can reduce risk during oral sex on a vulva or anus

HIV prevention medication

PrEP (pre-exposure prophylaxis) taken before potential HIV exposure, and PEP (post-exposure prophylaxis) started within 72 hours after a high-risk exposure, are highly effective when used as directed.

Daily oral PrEP or other approved regimens can reduce sexual HIV risk by more than 99% when taken correctly
PrEP does not protect against other STIs — combine with condoms and regular testing
PEP must start within 72 hours of exposure — sooner is better; go to an ER or sexual health clinic
Ask a PCP, sexual health clinic, or telehealth provider whether PrEP fits your situation

Vaccination

Vaccines cannot prevent every STI, but they dramatically reduce cancer risk from HPV and protect against hepatitis B — a sexually transmissible virus that can cause chronic liver disease.

HPV vaccine (Gardasil 9) protects against strains that cause most cervical cancers and genital warts
Hepatitis B vaccine is recommended for adults at increased sexual or blood-borne risk
There is no vaccine yet for HIV, herpes, chlamydia, gonorrhea, or syphilis
Discuss catch-up vaccination with a clinician if you missed adolescent doses

Regular testing

Many STIs cause no symptoms. Testing finds infections early, enables treatment, and reduces onward transmission — making screening a core prevention tool, not only a diagnostic one.

CDC guidance often recommends at least annual screening for sexually active people under 25 and others at increased risk
Test more often (for example every 3 months) with multiple partners or inconsistent condom use
Include throat and rectal sites when those exposures apply
Retest after treatment and when starting a new relationship

Communication and consent

Talking about testing, barriers, PrEP, and boundaries before sex is one of the most effective — and underused — prevention strategies.

Ask about recent testing and share your own status without shame
Agree on barrier use and backup plans if a condom breaks
Discuss PrEP, U=U (undetectable = untransmittable), and vaccination status when relevant
Consent includes ongoing agreement — either person can pause or stop

Partner strategies

Mutual monogamy after both partners test negative, limiting the number of concurrent partners, and supporting partners through treatment all lower community and personal risk.

Get tested together before stopping barrier use in a new relationship
If diagnosed, notify recent partners so they can test and treat
Avoid sex until you and partners complete treatment for curable STIs
U=U: a partner with HIV who is undetectable on treatment cannot sexually transmit HIV

Safer sex practices that make a difference

Small, consistent habits reduce risk more than occasional perfect use of one method alone.

Use lubrication

Adequate lube reduces condom breakage and microtears in tissue that can increase STI and HIV risk — especially for anal sex.

Avoid sharing sex toys without cleaning or barriers

Cover toys with a new condom between partners, or wash thoroughly with soap and water (or follow manufacturer guidance) before sharing.

Do not douche before or after sex as “protection”

Douching can disrupt natural flora and irritate tissue. It does not prevent STIs and may increase susceptibility.

Be cautious with substances that impair judgment

Alcohol and drugs can make consistent condom use and consent conversations harder. Plan ahead when you can.

Treat symptoms promptly — do not wait them out

Unusual discharge, sores, burning with urination, or unexplained rashes deserve a clinic or PCP visit. Early treatment prevents complications and spread.

Keep emergency plans for condom failure

If a condom breaks, consider emergency contraception if pregnancy is possible, and discuss STI risk — including PEP for high-risk HIV exposures within 72 hours.

Vaccines that prevent STI-related disease

Two vaccines are especially important for sexual health: HPV and hepatitis B.

HPV vaccine

Gardasil 9 protects against nine HPV types linked to most cervical cancers, many other cancers, and most genital warts. It is most effective before sexual debut but can still help adults who have not been exposed to all covered strains. Ask your clinician about eligibility and dosing.

HPV guide

Hepatitis B vaccine

Hepatitis B spreads through sexual contact and blood. A complete vaccine series provides long-term protection. It is recommended for many adults at elevated risk and is widely available through primary care and clinics.

Testing Center

PrEP and PEP — medication that prevents HIV

Antiretroviral medicines can stop HIV before or after an exposure when used correctly.

PrEP (before exposure)

Pre-Exposure Prophylaxis is medication taken by HIV-negative people to prevent infection. Options include daily pills and, for some people, other clinician-prescribed regimens. You need an HIV-negative test before starting and regular follow-up labs. PrEP is a powerful HIV tool — not a full STI shield.

HIV, PrEP & PEP

PEP (after exposure)

Post-Exposure Prophylaxis is a 28-day course started within 72 hours of a potential HIV exposure. Go to an emergency room (ER) or sexual health clinic as soon as possible. Do not wait for symptoms — HIV prevention after exposure is time-critical.

Exposure Center

Common myths about safer sex

Clearing up misunderstandings helps you make better choices.

“If we both look healthy, we do not need condoms.”

Most chlamydia, gonorrhea, and many HIV and herpes infections cause no obvious symptoms. Appearance is not a status check — testing is.

“Withdrawal / pulling out prevents STIs.”

Pre-ejaculate and genital skin contact can still transmit infections. Withdrawal is not a reliable STI prevention method.

“Oral sex is completely safe.”

Gonorrhea of the throat, herpes, syphilis, and HPV can all spread through oral sex. Barriers and testing of throat sites matter when oral sex is part of your life.

“Birth control pills protect against STIs.”

Hormonal contraception prevents pregnancy, not STIs. Use condoms or other STI prevention alongside contraception when needed.

“PrEP means I never need condoms or testing.”

PrEP targets HIV only. Condoms and regular multi-STI screening remain important for chlamydia, gonorrhea, syphilis, and others.

Already had a potential exposure?

Prevention is the long game. If something already happened, assess your risk and testing windows next.

Use Exposure Checker Testing Center