Vaccine Safety


man with safety glasses and liquid

Vaccines, like all medicines, must go through several stages of rigorous testing before they are approved for use in Canada. Vaccines are held to the highest possible safety standard in healthcare. See the following links for more information:

Canadian Center for Vaccinology

Canadian Immunization Guide

Immunize Canada

Vaccine Safety is Important to All of Us:  Information for Parents


Side Effects/Adverse Events Following Immunization (AEFI)

sad girl at school

Sometimes people respond to immunizations in unexpected ways. An Adverse Event Following Immunization (AEFI) is any adverse medical event that happens after an immunization, regardless of whether the immunization caused it or not. The most common side effects that happen after getting a vaccine are soreness, redness, and swelling at the place where the needle went in. Sometimes people develop a low grade fever – this means your body is doing its job and is responding to the vaccine. Some  people, particularly younger children, are more tired and irritable than usual; headaches can also happen.  Ask your healthcare provider what to look for after getting a vaccine. For more specific details on each vaccine, go to our Diseases That Vaccines Prevent page.

A small number of people do have more serious reactions to vaccines. If you notice something that concerns you or that you think is serious, see a healthcare provider. Allergic reactions like hives (blotchy, red, raised areas), wheezing, or swelling of the face and mouth are extremely rare. If you notice any of these symptoms, go to an emergency department. Otherwise, see your healthcare provider. Your healthcare provider will assess you to see if this is related to the vaccine or if you have another underlying condition. 

Serious reactions are very rare, but when they do occur, it is important that they are reported to Public Health. When they are reported, the health care system can track how many people have reactions to a specific vaccine. The vaccine is pulled from the market if it is connected to serious reactions and the risks of the vaccine outweigh the benefits.

Just because something happens shortly after getting a vaccine is given does not necessarily mean it was caused by the vaccine. For example, if someone eats an apple and then loses a tooth later that day, that does not necessarily mean the apple caused the tooth to fall out. The two events are linked because they happened close together (correlation), but that does not mean that the apple was the cause of the tooth loss (causation).

When making decisions about vaccines, it is important to evaluate risks vs. benefits. Although no medical intervention is 100% risk free, the chances of having a serious reaction to a vaccine are very small. Learn more about evaluating risks when you make decisions about vaccines.

Myth or Fact?

red question marks

Vaccines seem to cause strong opinions. Some people have voiced concerns about vaccines and autism, overloading the immune system, and vaccine ingredients, among other things. There is scientific evidence that supports giving vaccines, and many studies have been done showing the safety and the effectiveness of vaccines. Browse the posters, pamphlets, and studies below for more information.

Vaccine Myths Poster

Immunization - Get the Facts

Vaccine Studies: Examine the Evidence

Health Care Triage - Vaccines Don’t Cause Autism

Vaccine Ingredients

recipe card

Some people are concerned about what’s in vaccines. Some of the names on the ingredient list sound scary. In Canada, vaccines cannot contain ingredients in amounts that will cause harm. For example, formaldehyde is used in some vaccines to keep the germ material from causing disease. Many people don’t know that formaldehyde is a naturally occurring substance that is found in the human body. In fact, there is more formaldehyde in your body naturally than you will ever find in a vaccine. Formaldehyde in large quantities would be harmful; however, the amount found in vaccines has been thoroughly studied and is safe. Remember, even water is deadly when someone has too much of it. Check out the poster below to see where else some vaccine ingredients are found.

Vaccine Ingredients Poster



Vaccines have saved more lives in the last 50 years than any other healthcare intervention. In the past, many children did not survive childhood. Today, parents in developed countries can expect their children to live long, relatively healthy lives. Immunization has played a significant role in this.

See the difference in disease rates before the vaccine and after the vaccine - Vaccines Work. Many of the diseases that used to be common are rare today. However, since more people are choosing not to immunize their children, some of these diseases are coming back. Learn more about what happens when immunization rates go down. Check out the timeline of vaccine history over the last 1000 years.

For more information contact