Hi,
If your son is spitting more forceful and the entire feed he is taking in ,then maybe you will have to keep an infection in mind.Observe him for a day or more.If he persists to vomit and develops a runny motion with
fever then probably he has got the gI bug.If at any time you feel he has refusal to feed and passing less urine you will need to show him to the docter immediately.
Bye
Take Care.