It's too late to get a flu shot -- takes 2 weeks for full immunity to kick in. Also, you can shed for a few days right after the shot, so if you are leaving soon, you could spread it to others. And, your arm may end up being sore! Mine was bruised and sore for about a week.
I just came back from a business trip and I think I packed well for it -- there were items I didn't wind up wearing, but I'm glad I had them as options. Just a few things that I have added to my standard packing list for future:
1) Feminine hygiene products!! It wasn't that TOM at all, but ... yeah. There is just something about air travel that seems to mess up one's cycle! Is it the change in air pressure? Or exposure to female traveler's hormones? I dunno. Such items can be expensive in hotels, and you don't want to ruin your vacation having to hunt down a drugstore. So bring some, just in case!!
2) A clean cloth handkerchief, for use if you need to iron anything. Don't trust the hotel iron no matter how high end the place is. Last thing you need is to ruin one of your favorite items because the iron hadn't been properly cleaned.
3) Didn't need it this trip, since I wore socks the whole time, but if some of your footwear involves bare legs/feet, then definitely bring some bandaids just in case. And it does not hurt to bring a pair of thongs. I have had vacations ruined because of feet swelling + blister issues that were bad enough, I couldn't get even my wide-width pumps and flats on my feet.
4) I also always travel with a small bulb syringe because cabin air pressure seems to clog my darn ears.
5) Pashmina to wear on the plane -- and wrap around your face in case anyone on the plane is coughing and sick.
Have fun!