concerned about zazu

i need to know if i'm being paranoid. as some of you might know i lost my baby sox 3-17-02. well, a couple days later i noticed zazu (the king kitty) had been throwing up. sox did this. so i go to vet. zazu had a cold and got antibiotics.we had to treat all the cats because it was contageous. also, i swithched their food. over a week. i mixed old and new. well zazu throwed up twice yesterday. just a little. one was a small hairball. the other clear. i don't know if i'm just being paranoid. i don't want to loose another cat. when i was there at the vet, i asked her "IS HE HEALTHY?" she said yes. keep in mind this was just 2 days after loosing sox. sox died of liver failure and was tested for many feline deseases. he was not contageous. my vet saw no reason to put zazu through blood work. i don't want to either if i'm just being over protective. what should i do?? he just got off the medicine 3 or 4 days ago. zazu eats good , plays, but i'm still worried. i can't say just how much i love this cat. he is 6. aranoid3

You mentioned that you switched food. A lot of the time, they will vomit if they don't digest that particular food as well. It could also just be a hairball that has been working it's way up. Unless it's a prescription diet, I would try going back to the food you had been feeding. I would start there and then keep an eye out and make sure and note how often he vomits.