What are the side effects of the H1N1 vaccine?

No side effect of the vaccine is experienced by everyone, and some people may experience no side effects at all, but there are some common reactions to the vaccine. The most common side effects are:

  • pain, swelling, or redness at the injection site
  • fatigue
  • headache
  • muscle and joint pain

Children may have a fever, drowsiness, poor appetite, or irritability after receiving the vaccine.

Serious side effects (i.e., ones that require medical care or cause lasting health problems) are rare: less than 1 in 100,000 people will experience a serious side effect.

Why is it important to report side effects?

The H1N1 vaccine was tested for safety and effectiveness before it was approved for use by the public. The Government of Canada and the vaccine manufacturer continue to monitor its safety, and encourage people to report serious or unexpected side effects that occur after having the vaccine. Reporting side effects can:

  • offer an early warning of possible vaccine safety issues
  • improve our understanding of vaccine side effects
  • help Canadians make informed decisions about immunization

How do you report side effects?

Contact your doctor if you have a side effect that is unexpected, serious (i.e., causes you to seek medical care or has lasting effects on your health), or worrisome to you.

Your doctor will advise you on how to manage the side effect, and may decide to report it. Print the side effect reporting form and bring it when you visit your doctor. The report will only show information about the side effect - your personal information will not be shared.

Trish Rawn, PharmD