How can I prevent HIV and STI transmission during vaginal sex?

HIV is spread during vaginal sex when HIV-infected semen, vaginal fluid, or menstrual blood comes in contact with the mucous membranes of the vagina or penis. Some STIs (e.g., gonorrhea, chlamydia, trichomoniasis) are spread the same way as HIV. Other STIs (e.g., herpes, syphilis, chancroid) are transmitted through contact with infected skin or mucous membranes.

In general, since there is more mucous membrane area in the vagina, and a greater possibility of small cuts in the vagina, people who have a uterus are more likely than people with a penis to get infected with HIV and some STIs through unprotected vaginal sex.

Teenagers and people entering menopause are at especially high risk for getting HIV and other STIs, because the tissue lining the vagina is more fragile at these ages. Cuts or sores on the penis or vagina raise the risk of HIV/STI infection during vaginal sex. Using an external or internal condom lowers your risk of getting HIV and STIs through vaginal sex.

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