It makes sense that he would be perfectly alright. The vaccinations introduce such a tiny amount of just spike proteins (not full viruses, just parts the body can recognize later in an infection) that they are only detectable by lab equipment. Here’s a published research detailing just such an experiment.. For anyone who just wants a summary:

• The authors needed to use tests with “ultralow detection limits” to keep track of the antigen (substance causing an immune reaction, in this case the spike proteins). Again, this is because there’s barely any proteins introduced - the goal is to train the body to recognize the full COVID virus and that really doesn’t take much at all.
• The body starts clearing out those tiny amounts of proteins within a few days of vaccination and they are undetectable not long after that.

So basically this is the equivalent of showing someone a wanted poster for a criminal over and over again. After a couple of times this guy’s body would have recognized the proteins and immediately got down to cleaning them out. They were never full viruses or at a level anywhere near a “natural” COVID infection. When people feel shitty after a COVID (or any other) vaccine, it’s because their bodies have sounded the alarm and activated defenses like fever, inflammation, etc. It’s not because the vaccine gave them an actual disease or somesuch.