Vasectomy involves cutting off a segment of the right and left vas deferens thus disrupting the transport of the sperms from the respective testicle to the prostate gland. This would result in the sperms never reaching the semen that a man ejaculates.
This has no effect on a man’s sex drive. Most men can’t tell any difference in their ejaculate after vasectomy. This is because the testicles only contribute 5% in terms of volume to the seminal fluid.