Skip to Content | Skip to Footer
  • Text Size:
  • decrease text
  • increase text
  • High Contrast:
  • Contrast


Facts vs. Fictions


Fiction #1: There are many serious side effects from vaccines.


  • Vaccines are among the safest tools of modern medicine. In Canada, serious side effects occur very rarely- less than once in every one million doses of vaccine. The vast majority of side effects from vaccines are minor and temporary, like a sore arm or mild fever.
  • No long-term effects have been associated with any vaccine currently in use. Any such claims have not been substantiated. Careful research into potential adverse effects is done prior to widespread use. Most vaccines have been in use in Canada for decades.
  • The requirements for vaccines approved for sale in Canada are stringent. Every vaccine lot is safety-tested by the manufacturer and by the Bureau of Biologics and Radio Pharmaceuticals at Health Canada.
  • The dangers of vaccine-preventable diseases are much greater than the risk from a serious reaction to a vaccine.
Fiction #2: Some vaccines can cause autism or sudden infant death syndrome (SIDS).


  • Vaccines are sometimes blamed for conditions that are poorly understood. A child's first year of life is a time of tremendous growth and development, and it is a time when serious problems may start to appear. It is also the time when most vaccines are given, but this does not mean that vaccines cause these problems.

 The measles, mumps, rubella (MMR) vaccine does not cause autism.

  • Medical researchers and scientists around the world have studied information collected over many years to see whether there is a link between the MMR vaccine and autism - a lifelong developmental disorder. They have not found any evidence of a link.
  • In Canada, children are vaccinated against many serious illnesses, including measles, mumps and rubella (German measles), because immunization is the best way to protect children against these illnesses. The vaccines that Canadian children receive, including the MMR, are very safe.

Thimerosal does not cause autism.

  • Countless medical studies have concluded that there is no connection between thimerosal and autism. In Canada, the only vaccine that young children currently receive containing thimerosal is for influenza.
  • The amount of thimerosal used in the influenza vaccine is very small and has not been shown to cause harm.
  • Canada's National Advisory Committee on Immunization (which includes recognized experts in the fields of pediatrics, infectious diseases, immunology, medical microbiology, internal medicine and public health) states that, "there is no legitimate safety reason to avoid the use of thimerosal-containing products for children or older individuals."

Vaccines do not cause SIDS.

  • Fortunately, we have learned that other factors, such as sleeping position and second-hand smoke, are linked with SIDS, and successful public education campaigns like Back to Sleep have helped to reduce the rate of SIDS in Canada.
Fiction #3: Some vaccines can cause autism or sudden infant death syndrome (SIDS).


  • It is true that immunization has reduced most vaccine-preventable diseases to very low levels. However, some of them are still quite common in other parts of the world.
  • Travellers can unknowingly bring these diseases into Canada, and if we are not protected by immunization, these diseases could quickly spread. Without the protection we get from vaccines, a few cases could very quickly become many cases.
  • Improved sanitation, hygiene and living conditions have made a difference, but disease rates only began to drop with the introduction of vaccines.
  • Experiences in other countries show that if we were to stop immunization, these diseases would come back.

There are two reasons for all Canadians to be immunized:

  1. To protect our children and ourselves - even if we think our chances of getting any of these diseases are small, they still exist and can infect anyone who is not protected.
  2. To protect others - when you immunize your children, you protect other children and the whole community.


Fiction #4 : Immunizing a child against multiple diseases with one needle can overload the immune system.


There are two practical reasons to immunize children against multiple diseases with one needle:

  1. Better protection against more diseases.
  2. Fewer needles, which is easier on children and parents.
  • Research shows that your child's immune system can easily handle more than one vaccine safely and effectively. These are called combination vaccines.
  • Before any vaccine in Canada is used in combination with other vaccines, an extensive testing process makes sure that it is safe for children to receive these vaccines at the same time.
Fiction # 5 : Many people who are immunized still get the disease, and this proves that vaccines don't work.


  • It is true that when there is an outbreak of a disease like measles, some people who have been immunized get sick. This leads to the idea that vaccines don't work.
  • No vaccine is 100% effective. Because each individual is different, about 10-15% of people vaccinated will not develop immunity to the disease.
  • For example, in a classroom of 100 children immunized against measles - 10 to 15 of them remain vulnerable to the disease.
  • But in a classroom of 100 children who have not been immunized against measles, the entire group is vulnerable to the disease.