re: Coworker's wife being difficult about birthday dinner

this one is pretty easy, just respond with " I understand your concern, but ultimately everyone's medical history is their personal business, and it's unethical of me to ask them to disclose it. If you don't feel comfortable with being out in a social setting then you should make whatever decision you need to for yourself." and leave it at that, if they show then be polite and don't get into a vax argument, if they send apologies and say they can't come then offer to get dinner together sometime in the future.