The vas deferens are the tubes that transfer sperm from the testis to the prostate, where it is mixed with semen before ejaculation.
Sex drive or libido is affected by your testosterone. This hormone is made in the testis before moving into the bloodstream. It is not transported inside the vas deferens. So cutting the vas will not affect the manufacture or transport of testosterone.
In short, a vasectomy will not decrease your sex drive. In fact, knowing that you have reliable contraception may increase your sex drive.
