Poor kitty... I once had a MC girl who actually got a strain of cat flu from her Tricat booster! She was extremely poorly, luckily we had lots of space then and none of the other cats caught anything, she was rehomed but died when she was six! She'd always been a tiny MC and I still wonder if she had been ill before we got her.
I have heard of that too - if the kitten is given a live vaccine and inhales the droplets or a litter mate is able to lick where the booster has been given then it is thought possible they can contract the virus.
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