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You should avoid getting your flu shot if you:

  • Have experienced a serious allergic reaction from a previous flu shot

  • Developed Guillain-Barre Syndrome within 6 weeks of a previous flu shot
    (Government of Ontario, 2019)

  • Children younger than 6 months of age are too young to get a flu shot (Ontario, 2020)

You should wait to get your flu shot if you have:

  • A severe acute illness with or without fever, in which case you should usually wait until the symptoms subside before getting the shot (Government of Ontario, 2019).

What side effects can occur after getting a flu vaccine?

It is much safer to get the flu vaccine than to get the flu. Flu vaccines are safe and well-tolerated. Side effects are usually mild and last a few days. Possible common side effects include:

  • Pain, redness and swelling at the injection site, headache, fever, muscle aches, joint pain or feeling tired. Possible side effects in children include irritability, drowsiness or loss of appetite (Toronto, 2020).

  • In rare cases, serious allergic reactions (anaphylactic) can occur. Seek medical attention if you have trouble breathing, rash or swelling of the face and throat. The risk of Oculo-Respiratory Syndrome or Guillain-Barré Syndrome after flu vaccination is very low, about one case in a million flu shots (Toronto, 2020).

Having a bleeding disorder or being on blood thinning medication is not a contraindication to receiving the flu vaccine. The flu vaccine is given as an intramuscular injection, which can increase your risk of bleeding at injection site after receiving the injection (GSK, 2020)


For more information, please go to




Government of Ontario (2019). Flu Vaccine Safety and Effectiveness. Retrieved from:!%2F

GSK (2020). FluLaval Tetra Monograph. Mississauga, ON: GlaxoSmithKline Inc.

Ontario (2020). The Flu.  Retrieved from:

Toronto (2020). 2020-2021 Influenza Vaccine Fact Sheet. Retrieved from:

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