Cat won't eat/drink x 2 days. Shots up to date. Vomited once.
Dehydration can quickly kill a cat. 2 days is too long for him not to have any fluids. Check gums..white like? Not good. Pull skin up at back of neck. If it stays up that is also a sign of dehydration.
Just got my cat back from vet, They suggest that just like the flu sometimes are stomaches need to wait it out. The pet know their own body, they will eat and drink when ready.
You need to take your cat to the vet since he is sick. He might be having a stomach infection and that is why he is not eating. The vet will give him medication that will help him heal.