Maybe he can't get vaccinated because of some health issues or whatever? It is very unlikely as he must be really healthy to play at this level but we don't know his private life and it's actually none of our business.
I hope he is treated as everybody: if he has a valid exemption for whatever reason then he has the right to be here right? However if he doesn't have a valid exemption then he shouldn't be here at the first place.
But how come he was able to come here if he was not allowed? Some people did a very bad job somewhere then!