Can the vaccine give me the flu?

No. The flu vaccine can't give you the flu. But you might develop flu-like symptoms — despite getting a flu vaccine — for a variety of reasons, including:

• Reaction to the vaccine. Some people experience muscle aches and a fever for a day or two after receiving a flu vaccine. This may be a side effect of your body's production of protective antibodies.
• The two-week window. It takes about two weeks for the flu shot to take full effect. If you're exposed to the influenza virus shortly before or during that time period, you might catch the flu.
• Mismatched flu viruses. In some years, the influenza viruses used for the vaccine don't match the viruses circulating during the flu season. If this occurs, your flu shot will be less effective, but may still offer some protection.
• Other illnesses. Many other illnesses, such as the common cold, also produce flu-like symptoms. So you may think you have the flu when you actually don't.