Might I suggest that you point your wife to resources which might help her better understand what you are going through.
Hopefully the anger is from feeling so lousy from the shot, but I should warn you that many do experience what is commonly called riba-rage, which is hard to explain but it seems like rage but it really has no particular focus. I think for me it's a combination of the meds along with the frustration and uncertainty which winds up expressing itself in fits of rage.
My wife has learned enough to know that it's best to just let me be until it blows over and she trys to explain to the kids that Dad is not mad at anything in particular, just not feeling well.
Another useful resource, if it's available, would be a local support group where often times spouses of those who have gone through, or ar going through, tx attend to help other spouse understand better what to expect.
Hope this helps.
Usually the first few shots are the hardest...take tylenol p.m. before taking that shot. You feel bad because you are kicking virus booty and it feels like the flu. Try and time your shot so you sleep thru the worst. And generally, one incident of manly bad behavior won't warrant a divorce...;o)