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Immunization benefits and safety

Learn about vaccine safety and how getting immunized protects you and your community.

Why immunization is important

When you get immunized (get a vaccine), it starts your body’s natural immune response to a disease. Your body begins to make antibodies that protect you against the disease before you have contact with it. This is the process of becoming immunized or building immunity.

Without a vaccine, your body likely does not have the antibodies to fight many of the diseases that vaccines can prevent. This means you and your family could get very sick.

Getting immunized lets you build immunity against disease, before being exposed to it. Immunization helps your body fight the disease faster and can prevent you from getting the disease. It also helps to prevent diseases from spreading to others.

Over the past 50 years, immunization has saved more lives in Canada than any other treatment, procedure, or policy against disease.

The impact of vaccines over the years.


Polio can lead to paralysis (not being able to move all or part of your body) and death. Before immunization, polio infected more than 5,000 Canadians every year. Thanks to the polio vaccine, between 2016 and 2020, there were 0 cases reported.


In children under 5 years and adults older than 40 years, 2 to 4 out of 10 people who get diphtheria can die. Before immunization, diphtheria infected more than 9,000 Canadians every year. Thanks to the diphtheria vaccine, between 2016 and 2020, the highest number of cases reported in any year was 10.


1 in 1,000 people with measles will get encephalitis (swelling of the brain), which can lead to seizures, deafness, or brain damage. Before immunization, measles infected more than 60,000 Canadians every year. Thanks to the measles vaccine, between 2016 and 2020, the most cases reported in any year was about 100.


If you get rubella while you're pregnant, it can cause loss of a baby during pregnancy or the baby may be born with disabilities. Before immunization, rubella infected more than 37,000 Canadians every year. Thanks to the rubella vaccine, between 2016 and 2020, the highest number of cases reported in any year was 1.

Invasive Hib

Hib can cause meningitis and lead to lifelong disabilities and death. Before immunization, invasive Hib infected more than 600 Canadians every year, and it was the most common cause of bacterial meningitis in children. Thanks to the Hib vaccine, between 2016 and 2020, the most cases of invasive Hib reported in a year was less than 20.

Pertussis (whooping cough)

In Canada 1 to 4 deaths are related to pertussis each year, most often in babies. Before immunization, pertussis infected almost 20,000 Canadians every year. Thanks to the pertussis vaccine, between 2016 and 2020, the most cases reported in any year was less than 4,000.

Healthy communities

When you and your family get immunized with a vaccine, you’re protecting yourselves and helping to build your community’s defence against diseases.

The more people in a community who are immunized, the less a disease can spread.

For immunization to protect your community from certain diseases, most people in your community need to be immunized. This is often called “herd immunity.”

Herd immunity is important to protect people who are at high risk of getting very sick—including young babies, older adults, people having cancer treatment or who have had an organ transplant—who cannot get a vaccine. They rely on those around them to get immunized to help protect them from disease.

By getting immunized, you’re helping to protect your vulnerable neighbours and your community.

Current as of: October 26, 2023
Author: Provincial Immunization Program, Alberta Health Services
Our work takes place on historical and contemporary Indigenous lands, including the territories of Treaty 6, Treaty 7 & Treaty 8 and the homeland of the Métis Nation of Alberta and 8 Métis Settlements. We also acknowledge the many Indigenous communities that have been forged in urban centres across Alberta.