Hi Abb, my DD didn't have any reactions to her vaccinations. Except that she had a lump on each thigh which was sore to touch.
I too would hold off on the Panadol unless you think he needs it afterwards. It is pretty fast acting. Maybe talk to the dr about kiddie Neurofen too - I have found that DD responds so much better to that when she has had high, uncomfortable fevers. And you only have to give it half as often!