It's A Myth

You can't get the flu from a flu shot. The vaccine is made from inactivated virus making it non-infectious. Some people may have soreness at the injection site and occasionally people can experience some malaise and muscle aches for a day or two, but they are not infected with influenza. These feelings may result from the vaccine revving up the immune system, or because the time of year when flu shots are given is a banner time for respiratory viruses of all sorts.