Vaccines for children: Deciding to vaccinate

Vaccination is one of the world's greatest public health achievements, along with sanitation, antibiotics and clean drinking water. For over 50 years, vaccines have helped prevent and control the spread of deadly diseases in Canada and abroad.

As a parent, it's normal to have questions about vaccines. Learn how vaccines work, why they are needed and how they are given to help you feel informed and confident about vaccinating your child.

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How vaccines work

Vaccines help lower your child's risk of infection. They work with the body's natural defenses to develop protection against a disease.

The main parts of a vaccine are called antigens. Antigens are either:

  • not alive and contain killed (inactivated) germs or their parts or
  • are alive and contain live but weakened (attenuated) germs

Once in the body, antigens cause the immune system to react by creating:

  • antibodies
  • immune memory

This helps boost your child's immune system. Your child's boosted immune system will help destroy the germ threat before it becomes dangerous, thereby preventing disease or lessening its impact.

If your child is not vaccinated against those germs, they can get very sick. This is because their immune system is not prepared to handle the germs, allowing germs to multiply and result in disease.

How vaccines are given

Most vaccines are given by a needle into your child's upper arm or thigh. Some vaccines, like the rotavirus vaccine, are given by mouth. There’s an influenza vaccine for children that’s sprayed into the nose.

A few vaccines, such as measles, mumps and rubella (MMR), protect against multiple diseases in one shot (3 in 1). Others are given separately. Your child's immune system can safely and effectively learn from more than one vaccine at a time.
For instance, babies can respond to 10,000 different antigens at any one time.

Vaccine effectiveness

Routinely provided vaccines currently available in Canada can protect your child against 15 serious diseases. Most of these childhood vaccines provide over 90% protection against the disease.

Vaccines are safe, but like any medication or supplement (including vitamins), vaccines can have possible side effects.

While most children develop strong immunity following vaccination, some children may only develop partial protection. There are several factors that can influence the effectiveness of vaccines, including the:

  • age of the person being vaccinated
  • overall health status of the person being vaccinated
  • person's immune response to the vaccine
  • degree of match between the vaccine components and the type of bacteria or virus circulating in the population

In rare cases, those who have developed only partial immunity after vaccination can become infected and develop disease. However, vaccination helps prevent severe illness and serious outcomes, including death.

Another way to protect those with partial or no immunity is through high vaccination coverage in the population. When large groups of people are vaccinated, they create community immunity (also known as herd immunity).

The more people who are vaccinated in the community, the lower the risk of infection for those who are not vaccinated and those who developed only partial immunity from the vaccine. This means that when you are vaccinated, you protect yourself as well as those around you.

Community immunity helps protect those at high risk of developing disease and severe complications or death, such as:

  • infants and children too young to be fully vaccinated
  • adults 65 years of age and older
  • people with health conditions that affect their immune system (such as those undergoing chemotherapy to treat cancer or other serious health conditions)

Vaccines have successfully and dramatically lowered the rates of disease in countries with strong vaccination programs. Some diseases, like polio, have been eliminated from Canada and the rest of the Americas because of vaccines. Unfortunately, polio, like other childhood diseases, continues to pose a threat due to its continued prevalence in other countries around the world.

When vaccination rates are kept at high levels in the population, the occurrence of disease is low and outbreaks are rare. On the other hand, when vaccination rates are low, disease rates go up and we are no longer protected from outbreaks and severe disease outcomes, including disability and death.

Why vaccines are needed

Some of the diseases that are preventable by vaccines (such as measles, mumps and polio) have no treatment or cure. Children can become very sick, suffer lifelong disability, or die due to complications of vaccine-preventable diseases.

Even with improved living conditions and modern hygiene, vaccines are still critical for the prevention and control of infectious diseases.

In addition to diseases such as polio that have disappeared from Canada, others are now rarely seen because of long-term high rates of vaccination in the population. Some of these include:

  • rubella
  • diphtheria

However, these diseases still exist elsewhere in the world. People who live or travel in countries where these diseases still occur may become infected. If this happens around the time of their return to Canada, there is a risk of introduction and spread of these diseases here in Canada. Maintaining high rates of vaccination against these diseases helps to prevent further spread and outbreaks.

Some examples include:


Worldwide, measles is still a leading cause of death in children (89,780 cases in 2016). One person with measles can very rapidly infect 12 to 18 people who have not had the vaccine.

Measles is a very contagious disease. You can catch measles walking into a room even 1 hour after someone with the disease has sneezed and left the room.


In Canada, infections like pertussis (whooping cough) are on the rise. This is a serious and life-threatening disease, particularly for babies. About half of all infected babies require hospitalization.


Tetanus is an ever present risk because it is caused by a germ that is found in dirt and dust everywhere. Anyone who has not been vaccinated can get the disease if they have an open wound and come in contact with these germs. Although the disease is rare in Canada, if not vaccinated, those exposed to tetanus bacteria can develop a serious and life-threatening illness for which there is no cure.

The best way to protect your children's health is to prevent these diseases in the first place by keeping their vaccinations up to date.

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Vaccination for COVID-19

Vaccination is one of the most effective ways to protect us against COVID-19. Vaccines will be available at no charge over the course of 2021 to everyone in Canada.

What you should know about vaccines for COVID-19

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