The same happened to Ashley when he was last in hospital except that I did not give the shot because he had only vomited once and at that point the temp was not that high.  However, he had had a blow to the head and it was the first injury he had had as such and not knowing for sure what can happen we took him in to be looked at.  They upped his stress dose to 75mg per day and this was not even touching the problem.  He just kept spiking a temp when the meds wore off.  So I asked them to raise it to 100mg per day in x4 equal doses and he recovered instantly.  He was running around the next day in fact. Sometimes they can under estimate how much a child needs as they are all different and you just have to play by ear really.  

I have never known Ashley need anymore than triple his every day dose normally--orally that is.  What he ended up on was x5 times more than that before it made a dent.