It's funny that you mention this because I had my thyroidectomy in Dec. and RAI in January and I'm just getting over the first cold I've had in 4 years.
My doctor told me that having cancer will weaken ones immune system. She recommended I get a flu shot this year, which I did. It was my first flu shot.Last year I didn't get the flu or colds, even without the shot, but didn't take any chances this year. She even recommended my husband get the shot, so as not to expose me.
Trish