Wolflady-

As far as care after stomach upset - the best thing to do is offer very small amounts of water and an easily digested food (homemade chicken and rice in a blender is really good). If they keep it down for four hours, offer a little more and a little more frequently until they're back to their normal feeding schedule. If at any time the vomiting starts again withold food and water for another four hours minimum. If you're worried about dehydration, pinch a little of their skin between your thumb and finger - if it snaps back, they're okay. If it stays pinched up or puckered up, they need to go to the vet for IV fluids.

As far as the reaction to the shots - I have heard of a reaction before, but the response is usually a stiff, wooden, hunched over posture, with little or no movement or interest in the world around them. It usually lasts about 24 hours. I have never before heard of the gastrointestinal reaction, though. I'm sure it was very distressing for both you and Marius. I'm glad he's better now.

The best way to handle that is to stagger their vaccinations by a few months, i.e. rabies in January, FeLV in March, Upper Respiratory in May. This would also enable you to identify which inoculation is the culprit, if it is only one. Most of the time, though, they can take them individually. You may even be able to stagger the years - the upper respiratory shots can be given every three years now, and the rabies vaccinations are also good for three years, but I live in a state that has a pervasive rabies problem, so it still has to be given every year here even though it is effective for three. I don't know how California's laws are, but this may be an option too. I think it might be good to consider another clinic, too, because this should have been discussed with you when it became clear that Marius was becoming ill from his shots. But, like you say, they may have just been extremely busy.

Anyway, I hope some of this helps.