Panleukopenia vaccine.

we have two 12 week old kittens. last week we looked after two 7 week old kittens for a relative. They had not been inoculated and came to us with diarreaha which we were told was because they had drunk milk. 2 days later we noticed that our kittens also had diarreaha so we immediately took all four of them to the vet. They were all given a worming tablet and sent home. That afternoon the two 7 week old kittens fell into a deep sleep. when we tried to wake them one was dead and the other wa unconscious. we took them back to the vet and she gave the unconscious one an injection and said it would not live the night. He recovered and the next day was eating playing etc. Two days after that he then became very larthagic along with our kittens. I took them all back to the vet the next day as ours had not eaten for days. She gave ours an injection that made them eat and seem better for a while and told me that the younger kittens had a virus but our cats would be ok as they had had the first inoculation. The younger kitten died that afternoon. (FRI) and half an hour later one of our cats had severe diareha and also seemed to be running away from his own behind. Since then it has been non stop and this afternoon (sun) the second cat also started to have it. we have phoned the vet but she just says it is because of the worming tablets but this just does not seem right to us, as they had these last tues. we are very scared that they have the same virus. should we listen to the vet or push for more treatment. Is it possible for a kitten to catch this virus after they have had a first innoculation. Please can you help us with this as we are extremely worried but vets in austria dont seem to understand how important they are to us.