Download Immunization / Vaccines What is a vaccine?

Immunization / Vaccines
What is a vaccine?
A vaccine is an injection of tiny amounts of one or more dead, weakened or purified components of viruses or
bacteria. A vaccination is intended to help your immune system defend against the viruses or bacteria if you come
across it in the future and to prevent any disease they may cause.
How does a vaccine work?
Vaccines help protect children and adults from diseases, often serious and potentially deadly ones, by preparing
their bodies to fight them. The injection of a weakened form of a virus or bacteria into the body causes the
immune system to produce specific antibodies to fight the virus or bacteria in the vaccine, allowing the body to
destroy these germs if they are ever encountered in the future.
The principle of vaccination is simple–that it is easier and more effective to prevent a disease than to treat it. Its
role in healthcare is to prevent infectious diseases and spare people from specific illnesses, and even to save
lives. Vaccines are responsible for helping control many infectious diseases that were once much more common
in North America and around the world, including polio, measles, diptheria, pertussis (whooping cough), rubella
(German measles), mumps, tetanus, and others.
A vaccine is designed to deliver just enough of a dead or weakened germ to have the immune system recognize it
as an invader, or antigen, but not enough to cause the signs and symptoms of a disease. The body then produces
proteins called antibodies that can fight the antigens. In fact, this process occurs hundreds, even thousands
of times daily with all kinds of germs, without us even noticing. Though the antibodies mostly disappear once
the invading antigens are destroyed, the cells that produced the antibodies remain, called memory cells. These
memory cells can recognize the antigen if it ever attacks again, even decades later–an effective form of protection
called immunity.
Who gets vaccinated?
Virtually anyone can get vaccinated. There are vaccines designed to protect newborns, infants, adolescents and
adults from a wide variety of different diseases.
For a small percentage of the population, vaccination or certain vaccines are not advisable. This includes:
•Children who are too young to receive a vaccine because it may cause the infection it is intended to prevent; i.e.,
children under a year cannot receive the measles vaccine
•Those who cannot be vaccinated for medical reasons, such as children with leukemia
•People who cannot make an adequate immune response to vaccination
What diseases can vaccines prevent?
The list of vaccine-preventable diseases is long, and constantly growing with new developments vaccine
research and development. It should be noted that between 10 to 15% of people who are vaccinated will not
develop immunity to the disease, though the risk of severe disease will be reduced. Below is an example of the
many diseases we can currently prevent with available vaccines, with routine vaccinations for Canadian children
highlighted in bold:
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Immunization / Vaccines
•Anthrax
•Pertussis (whooping cough)
•Cervical cancer (human papillomavirus vaccine)
•Diseases caused by pneumococcal bacteria
•Diptheria
•Polio
•Hepatitis A
•Rabies
•Hepatitis B
•Rotavirus
•Haemophilus influenzae type b disease
•Rubella (German measles)
•Influenza
•Smallpox
•Japanese encephalitis
•Tetanus (lockjaw)
•Lyme disease
•Typhoid
•Measles
•Tuberculosis
•Meningitis
•Varicella (chicken pox and shingles)
•Monkeypox (actually the smallpox vaccine)
•Yellow fever
•Mumps
Some common misconceptions about vaccines
The widespread use of vaccination for decades now has lead to the virtual disappearance of previously common
illnesses in Canada and many countries around the world. Diseases like polio and diptheria are rarely seen in
this country, which speaks to the success of the process. Still, there are opponents to the universal practice of
vaccination, which has lead Health Canada and other international agencies to address certain concerns they
consider as misconceptions.
Here are a few of the issues they cover on their website:
“Vaccines are not safe.”
According to Health Canada, vaccines are among the safest of modern medicine’s tools. Though vaccination can
cause minor and temporary reactions such as swelling or tenderness at the injection site, or a mild fever, serious
side effects are very rare. An example of this is the rate of severe allergic reaction to vaccination: fewer than one
case for every 100,000 doses of vaccine given. Considering the dangers of vaccine-preventable diseases, the
benefits of vaccination far outweigh the risks.
“Vaccines are linked to chronic diseases such as autism, multiple sclerosis (MS), asthma, and Crohn’s disease.”
Based on recent research using sound scientific methods, and reviews of studies from around the world, there is
strong evidence that this statement is false.
“Vaccines weaken the immune system.”
On the contrary, vaccines actually strengthen the immune system to protect Canadians young and old from
specific diseases. Besides, the memory cells that vaccinations create in the immune system to recognize these
diseases represents only a tiny portion of the body’s total capacity.
“Vaccines are not necessary because the diseases are gone.”
Just because a vaccine-preventable disease is uncommon in Canada, doesn’t mean you can’t catch it. With
international travel, a disease can be brought into the country, and people can arrive in areas where the disease is
common. Also, being vaccinated helps prevent disease transmission to those people who cannot be immunized
due to severe allergies or certain medical conditions–meaning the protection goes beyond yourself.
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Immunization / Vaccines
Proof of the risk of being overconfident about disease risk comes from both Russia and Japan. In 1974, 4 in 5
Japanese children were being vaccinated against whooping cough. By 1976, that number dropped to 1 in 10
due to rumours of it being an unsafe and unnecessary vaccine. In 1979, a major epidemic of the disease hit, with
more than 13,000 cases, compared to under 400 in 1974. 41 deaths were reported, and vaccinations began in
earnest again by 1981, with excellent results. In Russia, much the same thing happened when organized diptheria
immunization was suspended. An outbreak hit in 1994, with over 5,000 deaths–this in a country that had only a
few cases per year when vaccination was routine, and no deaths.
“Vaccines contain toxic substances.”
Before being released for public use, every vaccine used in Canada is tested for quality and safety. Some vaccines
still contain a slightly controversial preservative called thimerosal, which has a minute amount of a less toxic form
of mercury in it. However, Canada’s National Advisory Committee on Immunization recently determined that “there
is no legitimate safety reason to avoid the use of thimerosal-containing products for children or older individuals.”
Resources
Helpful information and support networks on the internet:
Health Canada (www.hc-sc.gc.ca)
Public Health Agency of Canada (www.publichealth.gc.ca)
Caring for Kids (Canadian Paediatric Society (www.cps.ca/caringrforkids)
Centers for Disease Control and Prevention (www.cdc.gov/vaccines/)
World Health Organization (www.who.int/immunization/en}
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