Gastroenteritis in puppy?

My puppy of 12 weeks has recently been vaccinated. One puppy recently dies of this same disease and now his brother is infected. He is walking around but has vomited twice and does not eat. I have given him 2ml of pro-kolin+ and 5ml of worm medicine(2nd dosage after a month) I am really worried and do not want to lose another puppy. I phoned the vet however he said to come tomorrow morning and I am not too enthusiastic to go to him since a few animals have dies after his consultations. Can anyone help me please?