Unscientific anecdotal self observation. Gargling for 5 or 10 secs. with balsamic vinegar and swallowing seems to help my sore throats within minutes. It is safer than whisky and tastes better than apple cider vinegar. It will burn for a few secs. In my case it seems to stop progression of infection down the throat to the upper respiratory tract. Laugh if you want . I am sure that you will get your son the best medical care possible.
I hope that your son has a speedy and complete recovery.