Vasectomy is a surgical procedure for male sterilization and/or permanent contraception. During the procedure, the male vasa deferentia are severed and then tied/sealed in a manner so as to prevent sperm from entering into the seminal stream (ejaculate) and thereby prevent fertilization.uring the procedure, the male vasa deferentia are severed and then tied/sealed in a manner so as to prevent sperm from entering into the seminal stream (ejaculate) and thereby prevent fertilization.