Possible side effects include:
- Fever (low grade)
- Soreness, redness or swelling where the shot was given
The intradermal (between the layers of the skin) flu shot may cause additional mild side effects, such as toughness or itching where the shot was given. Side effects typically begin soon after the shot is given and usually last one to two days. Life-threatening allergic reactions are very rare. If any unusual condition occurs following vaccination, seek medical attention right away.