How immunization works:

• exposing the immune system to vaccines which contain germs or parts of germs causes the immune system to respond just like it does for infection
• the body makes the same antibodies it would in response to infection
• immunization triggers immune memory without the risk of illness or death associated with infection. The body can fight off the specific germ if an exposure occurs
• vaccines like all medicines must go through a series of steps before their use is approved for the public
• vaccine safety is taken very seriously by health authorities in Canada, including the provincial and federal governments and the Canadian Paediatric Society
• before a vaccine is approved for use it must be shown to be safe and effective in preventing the disease for which it is intended.

DEFINITIONS

Bacteria

• microscopic organisms that are able to live on their own provided they have essential chemicals to nourish them

Viruses

• microscopic organisms that are unable to live on their own
• to grow and reproduce, viruses must get inside of cells

Antigens

• bacteria and viruses have unique proteins and complex sugars on their surface called antigens
• antigens enable the germ to stick to human cells
• the immune system targets bacterial and viral antigens

White blood cells

• special blood cells (T-cells) help the immune system kill germs along with antibodies

Immune system

• a system in your body that helps to recognize and fight infection and foreign substances in the body

Immune memory

• the immune system has a strong memory that enables it to recognize foreign substances that enter the body even if the exposure occurred many years before
• immune memory is particular to specific germs and it does not mean that immune memory has been developed for all types of germs

Incubation period

• the time between when a person is infected with a bacteria or virus and the onset of symptoms. This varies for each germ.

Chronic carriers

• persons who carry a virus in their blood but do not have any symptoms of illness