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Vaccines & Immunization

Immunization is one of the most important advances in public health and is estimated to have saved more lives in Canada over the past 50 years than any other health intervention.

Immunization programs help to prevent, control, eliminate and eradicate vaccine preventable diseases. 

Immunization directly protects individuals who receive vaccines. Through “herd immunity”, immunization against many diseases also prevents the spread of infection in the community and indirectly protects:

  • Infants who are too young to be vaccinated,
  • People who cannot be vaccinated for medical reasons.
  • People who may not adequately respond to immunization.

People need to be immunized even though some vaccine preventable diseases no longer exist in Canada. Immunization programs have reduced the number of cases and/or deaths resulting from many serious diseases.

Bacteria and viruses that cause vaccine-preventable diseases are still present in Canada or in other parts of the world. Even if a disease is uncommon in Canada, travellers can bring illnesses back to Canada and infect people who are not vaccinated.

Unless a disease has completely disappeared worldwide, there is a risk that a small outbreak can turn into a large epidemic if most of the community is not protected.


Vaccines used in Canada are highly effective and extremely safe.

Prior to authorization for use in Canada, vaccines are extensively tested. Manufacturers must submit scientific and clinical evidence that demonstrates the safety and efficacy of the vaccine.

Health Canada supervises all aspects of vaccine production by manufacturers to ensure safety, effectiveness and quality. Vaccine safety continues to be rigorously monitored and evaluated after the vaccine is on the market.

All vaccines can have mild side effects, which are minor and temporary, such as a sore arm or a slight fever. Most side effects resolve within 72 hours of vaccination, unless vaccinated with live-attenuated vaccines. Serious side effects, such as severe allergic reactions, are very rare. In Canada, the rate of serious side effects from childhood vaccines is about one per million doses of vaccine.