not sure if thermometer issue, but bcos of different thermometer reading, I use that as my 2nd opinion, first would be my instinct (2nd time mother here), if I see my baby have unusual behaviour after vaccination, (she is a happy baby, hardly crying), but when she cries a lot for no reason, her backside is warmer than forehead also, I know that somehow she is uncomfortable, so I gave her paracetamol to ease her inner pain (as prescribed by her PD)