[Ellie May]

Any vomiting, diarrhea, pale gums?

Lethary and tiredness is normal but he should be okay by now.
If he isn't better soon, I'd call the vet.

Side effects could probably include anything you could think of like vomiting, diarrhea... but long-term side effects to vaccines that aren't normally talked about could be autoimmune disease, cancer, vasculitis...

Any gum color other than pink, go to the vet immediately.