My son is 2 and has SWCAH.  We only double his dose unless he has a very high fever then we triple.  It just depends on the illness.  We have been lucky the only stomach virus he has had was one with diarrhea; he has never had a vomitting virus.  He only recently had the shot for the first time, and that was due to a broken arm.  I believe that each kid is different, and must be treated on an individual basis.

Thanks,

Carrie