Ladies, do you take any immune boosters when it is flu season? What are they?

Here, we increase our Vitamin C intake and drink lots of water whenever there is a change in season. I take multivitamins daily and also a separate vitamin D pill to keep my energy up especially during the darker days. So far it's working, compared to my partner who doesn't take any vitamins, I havent gotten sick in a year. It could be the placebo effect like what Hui Qun mentioned but whatever it is, I'm not going to stop anytime soon.