How do you get the flu when you already got a flu shot?
There are many different types of flu and the seasonal flu shot only prevents three of the most likely to be circulating flu viruses. So if you happened to get exposed to a type of flu that wasn't in the vaccination, then you could get sick from it.Another reason might be that you caught the flu before you got the flu shot and so there was not time for the shot to work before you got sick.Another reason might be that you got the shot and then were exposed to the flu before your immune system could give you immunity from the vaccination. It takes around two weeks after getting the vaccination for an adult to have full immunity from it. For children under 10, a series of two vaccinations are needed given approximately a month apart, then it takes another few weeks before the body has developed the full immunity, so exposure during any of those time frames before full immunity can cause illness in those children.