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About Immunization

Immunization is a proven public health measure that helps control and eliminate very serious and life-threatening infectious diseases. According to the World Health Organization (WHO), immunization "is the process whereby a person is made immune or resistant to an infectious disease, typically by the administration of a vaccine. Vaccines stimulate the body's own immune system to protect the person against subsequent infection or disease." While immunity can also be achieved through natural exposure to wild type virus, this comes at the risk of serious disease, hospitalization and potentially even death. 

  • It is estimated that 2 to 3 million deaths are prevented each year by current immunization programs and vaccines.
  • The Public Health Agency of Canada (PHAC) credits immunization as saving more lives in the last 50 years than any other health measure.

How Vaccines Work 


Nature infection from certain diseases can kill or seriously harm an individual before their body is able to mount an effective immune response. Vaccines on the other hand trigger the body's natural immune response to produce the necessary antibodies before exposure to the wild type virus. This way, if exposed to the wild type virus, the body has the necessary antibodies to fight off the infection.

Antibodies and the Role they Play

Vaccines contain tiny amounts of material that make the immune system produce certain proteins called "antibodies". Antibodies can attack and destroy viruses and bacteria.

The immune system stores this information on how to make these antibodies. Later -- even many years later -- when the body is exposed to that same bacteria or virus, it "remembers" how to make these antibodies. The body produces those antibodies again, stopping the virus or bacteria from causing illness.  

Immunization Protects Us All

Immunization protects both individuals and the larger population by preventing the spread of infections. It is important to achieve and maintain high immunization coverage in order to provide the best protection against vaccine preventable diseases.
Last Updated: September 18, 2014