Parvo is my first thought...You need to get him to his Vet ASAP.....If it is Parvo, time is of the essence & treatment must begin immediately......Make the call....Good luck & let us know what happens.....Karla
Agree, it is parvo until proven otherwise! He will need lots of supportive care to get through this, but it can be done. They usually take 1-2 weeks of fluids and antibiotics among other things. Avoid contact with any other dogs; the dog and anyone in your family that has contact with your dog. The virus is extremely contagious and can only be killed on surfaces with bleach.
Totally agree especially since shots are not complete. Better to be safe than sorry.