My husband had a vasectomy 8 months ago what are the chances it didn't work?

Very unlikely: The success rate for vasectomy is well above 99%. If there is any doubt, he needs to have a semen analysis.

VERY low.: Vasectomies are nearly 100% effective. A uk study from 2004 reported a failure rate of 0.5%, or 1:2000. These data were gathered after men were given the a-ok to not use other protective measures because their semen analysis showed no sperm.

Who knows?: The success rate of vasectomy (meaning no more sperm in post-vasectomy semen) is above 99%. But it still cannot speak for an individual's success; so, be realistic, face it, and live on. Best wish...