My work did flu shots about six weeks ago and I wasn't allowed to get one as I was in the tww and didn't know whether I was preg or not (turned out not to be). The nurse said no studies have been done on the effects of the vaccine during any stage of pregnancy so said it was best not to, just in case. She said I wouldn't be able to live with myself on the off chance something happened to a bub I may have been carrying.

Hope that helps.