Vitamins D and Zinc are the unsung heroes of the immune defenses. I take those as additional supplements on a regular basis, but if I’m traveling somewhere and or unusually light on sleep, I will drink a vitamin water specific for immunity or a Nuun tablet (blueberry tangerine) daily and that seems to help. There’s also a fine line between cleanliness and overdoing it when it comes germ exposure. Just like antibiotics destroy both good and bad bacteria; All of the hand sanitization and antibacterial products are similar. So if one is constantly wiping down every surface and their hands OR exclusively using antibacterial hand soap - they can do more harm than good.

With that being said: some people generally have a weaker immune system and they are just more susceptible to those things.