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Frequently Asked Questions:  Influenza Immunization

Are vaccines safe?

Vaccines are safe and effective. Vaccines are developed to meet the highest standards of public health. 


Vaccines are continually monitored for safety and effectiveness both in Canada and around the world before they are approved for use.


How do vaccines work?

Vaccines protect people from disease by putting a portion of a bacteria or weakened virus into the body to trigger an immune response, just as though you had been exposed to a disease naturally.


Vaccines work because they trick your body into thinking it is being attacked by the actual disease, so it produces antibodies to protect you. The bacteria or virus in a vaccine won’t make you sick. Instead, the vaccine prepares your body with antibodies that act as a defense and protects you against the disease and the potential complications that can be caused by that disease.


What ingredients are in vaccines?

The ingredients in vaccines all have an important role to play to make sure the vaccine remains effective and safe. 

All the ingredients in vaccines are found in small quantities and can be found naturally in the food we eat and in nature. The main ingredients of a vaccine are dead or weakened viruses or bacteria.


Vaccines can also contain adjuvants, which help the body’s immune system respond better to vaccines and additives and preservatives to help maintain the quality and effectiveness of the vaccine.


Will multiple injections overwhelm the immune system?

Every day our bodies encounter millions of germs, causing our immune systems to work continuously to protect us.

Therefore, exposure to the parts of weak or dead viruses or bacteria in vaccines is easily handled by our immune systems. In fact, our immune system needs to be challenged continually to stay vigorous.


Can you get sick from vaccines?

Vaccines cannot make you sick and you cannot get the flu from the vaccine.


Do vaccines cause a severe reaction?

Just like any medication, vaccines can cause some reactions. Some people may experience mild reactions from vaccines, including pain, redness or swelling at the injection site; or mild fever after the vaccination.


Depending on the vaccine received, some people may also experience a mild rash, fatigue, or aches. All these are common reactions and resolve in a few days.


Severe reactions, such as an allergic reaction to a vaccine, are rare. If you or your child has had a serious allergic reaction to a previous dose of a vaccine, please talk to your health care provider.


Do vaccines cause autism?

Vaccines do not cause autism. Medical researchers and scientists around the world have not found a link between vaccines and autism.


What is community immunity?

Immunizations protect not only the people who get immunized. They protect the people around them, too.


When most of the people in a community have been immunized against a contagious disease, it greatly reduces the spread of disease and the chance of an outbreak of that disease. This is called community immunity, or herd immunity. 


If fewer people get immunized, it will be much easier for a contagious disease to spread. And diseases that may not be serious for adults can do serious harm to small children.


Community immunity protects newborns who are too young to be immunized, people who cannot be vaccinated for medical reasons (immunocompromised, organ transplants, cancer treatment, allergic reactions), and people with weaker immune systems, such as the elderly. For these groups, community immunity is vital.


What is Seasonal Influenza (the flu)?

Seasonal Influenza information for health professionals

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