He had the Astrazeneca vaccine three weeks today and was very pleased to have it. He had a slight headache after it and said he felt extra thirsty, but that was all. For the last week he's felt unwell and says in the last few days he's really declined with shivering, all over body aches and pains, feeling sick etc.
He's not the type to ever go to the doctor and is almost never ill so I can't help being a bit worried. He's said if he doesn't improve by Monday he'll book Monday off and see a doctor. He's been wanting the vaccine since forever and now is actually saying he wishes he hadn't had it. 
This is not to put anyone off the vaccine, but it's just out-of-character for him. For context, he's early 50s, has sleep apenea and uses testoreone gel, but no obvious underlying health issues.
I can't observe what he's like as I live 3 hours away. Hopefully it's nothing, but are side-effects several weeks after the vaccine normal or something to be concerned about?