. Condoms are the only form of contraception that protect against most STIs as well as preventing pregnancy. . A diaphragm is inserted inside the vagina to stop sperm from getting in. They do not protect against STIs.. Hormone implant placed under the skin in your upper arm by a doctor or nurse. It releases the hormone progestogen into your bloodstream to prevent pregnancy. It does not provide protection from STIs.. Vasectomy do not protect from STIs. Semen can still carry STDs, even if it doesn’t contain sperm.