First let me begin by saying welcome!  You will definately find loads of support and lots of helpful information here!

Now, to your question.  Are you absolutely sure that your son is vomitting or is he spitting up?  I ask because there is a definate difference between the two.  I speak only from experience with my salt-wasting CAH son.  When he was an infant he was a big time spitter.  He would spit up pretty much throughout the day (we actually laugh at the pictures we have in which it appears he was always wearing a bib!)  Spitting up for my son was more like oozing, he never projected.  I was told that in his case (remember each child is different) that if projected it was then considered vomitting. 

I know that it can be tricky with giving meds so here is what we did.  First, we would time his feedings and meds so that there was a least a hour between.  Hopefully then if he spit up we were sure the meds were already working in his system.  Secondly, if he did spit up right after receiving his cortef we would give his dose again.  This worked extremely well for him.

As to whether or not his spitting up was related to the cortef (he was on the liquid at the time), well I guess we will never know for sure.  Because, now this is best news, they do outgrow spitting up.  By the time my son was around seven months he just stopped, as simple as that.  Needless to say giving him his cortef became much, much easier.

I hope this was of some help to you and your wife.  Good luck with your new baby ~ enjoy every minute because it definately goes toooooo fast!!