@Jennyanydots - I have done some research into this and it seems some studies say there are slight increases in the risk of mild diseases, but nothing conclusive. I read one mans journey through researching his own vasectomy and he raised some interesting points, mainly in regards to lifestyle choices. He basically said that if he ate a clean diet and exercised enough, had enough rest and respected his body then a vasectomy should not alter his chances of inheriting an autoimmune disease post vasectomy.
My husband is only 24 and here in nz they won't allow him to have the procedure as they think he needs to be 30 before making a permanent decision, the same goes for tubal ligation. So unfortunately we will probably be heading back down the route of oral contraception.