A vasectomy is a minor procedure that blocks sperm from entering the semen. It is more than 99% effective after follow-up testing confirms there are no sperm in the semen, with less than 1 out of 100 couples becoming pregnant in a year. Many people choose it because it is highly effective, hormone-free, and does not require ongoing pills, devices, shots, or refills. It does not work immediately, so backup birth control is needed until semen testing confirms it is effective. Because it is intended to be permanent, the decision usually comes down to wanting a long-term option versus the possibility of wanting future fertility.