The flu shot is only effective against 40% of the flu bugs going around this year.
If you've had the vaccine, don't rely on it to protect you--wash your hands with soap and hot water, using a clean towel to wipe them off. Wash them frequently. If you are in a public place, don't touch your face--hand-to-face contact is how you get sick. Hand sanitizer is next to useless, by the way. Real soap, hot water. Clean towel.
If you are a manager or boss, don't be an ass: Let your sick employees stay home instead of coming in and infecting everyone. Productivity isn't helped by making a sick, miserable worker stay and make everyone else sick and miserable (and unproductive). A couple days for them to fight it off will be better than their bodies dealing with the stress of work while rallying against the virus.
As a customer, it looks bad to me if your employees are serving me while they are sick. It tells me that, not only do you not care enough about your workers to give them the time off they need to heal, you also don't care if they come in and spread the disease around to your customers.
Good luck everyone, and stay well.