YES. Latex or polyurethane condoms block the smallest organisms and even large particles like sperm. They help to prevent most major STIs. A few STIs, such as herpes, human papillomavirus (HPV), and syphilis, can sometimes infect places on the body not protected by condoms. If you or your partner notice sores in the genital area, you should not have sex. Call your doctor or health care provider for an exam immediately.