I know this thread is asking for prayers (not ways to convince him) but I just want to say -- any opposition should be kept very short and sweet.
If I had a son in this situation, I would keep it very simple. The Han Solo argument: "What good is a reward if you ain't around to use it, kid?"
What good is a job -- even a career, a pile of money, a huge nest egg -- if you lose your health, suffer debilitating injury, even death, due to this poison injection?
What is that job for? To save your soul? If it's not, it shouldn't be placed ABOVE concern for your health. Oh, that job is how you get health insurance? Well, take the vaccine, and you'll be spending PLENTY of time at doctors and hospitals. Frankly, I'd rather NOT NEED health insurance (due to excellent health) and have no health insurance, than need health insurance badly (due to using it all the time) AND have it.
If it's for "being able to live on earth, survival, being able to stay fed & healthy, being able to get married, have a family" -- then DON'T TAKE THE VACCINE AT ANY COST because you can kiss those things goodbye if you DO take the vaccine.
There is only ONE good reason to allow your health to be destroyed: eternal life with God. If taking the vaccine earned you heaven, even death would be a small price to pay. BUT THAT'S NOT WHAT THEY ARE OFFERING.
Taking a vaccine that will separate your soul from your body -- or render your body near useless -- in order to "keep body and soul together" (earn a living, have a career) is shortsighted at best, and extremely foolish at worst.