<prompt> A couple is advised to use barrier methods after vasectomy till :3 monthsNo sperms in ejaculateNext 15 ejaculationsNone of the above  <response>: It is imperative that some other contraception should be used for the next three months or 15 ejaculation. At the end of the period semen analysis should be done to confirm the absence of sperm in the ejaculate. TEXTBOOK OF GYNECOLOGY SHEILA BALAKRISHNAN SECOND EDITION PAGE NO 396 