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Frequently Asked Questions

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Do vaccines work?

Vaccines work very well, indeed. We know that in countries where vaccination rates are high, disease rates are low. We also know that the opposite is true. In countries where vaccination rates are low, disease rates are high.

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Vaccines prevent millions of deaths

The World Health Organization (WHO) and similar organizations are convinced that vaccination gives many more benefits than it costs. The WHO estimates that every year, more than two million deaths are prevented worldwide due to immunization.

The World Bank has stated that countries around the world should FIRST invest in vaccination programs when they are setting up public health programs.

In the Decade of Vaccines 2011-2020, the World Health Organization (PDF Document) hopes to see "a world in which children, families and communities enjoy lives free from the fear of vaccine-preventable diseases…access to safe and effective vaccines is a human right".

Vaccines really prevent disease

Before the development of measles vaccine, about 300,000 Canadian children under the age of 18 were affected by measles. The disease caused almost 300 deaths each year and left another 300 individuals with brain damage.

After the measles vaccine was introduced, the number of cases decreased drastically to an average of less than 50 cases of measles each year in Canada.

Another example of the impact a new vaccine is the reduction in the number of person getting sick or dying from pertussis (Whooping Cough) following the widespread use of the Pertussis vaccine in the mid 1940's. The number of people getting sick dropped from 50 000 cases to 3000 cases per year. The number of deaths was also reduced from 100 deaths per year to between one and five persons dying per year as a result of the Pertussis disease.

Other vaccine successes:

  • In North America, diphtheria vaccines reduced the diphtheria-related deaths by more than 99%.
  • Before the varicella-zoster virus (VZV) vaccine was introduced, almost 350,000 cases of chickenpox occurred annually in Canada. There were 53 deaths due to chickenpox between 1987 and 1996. A vaccine is now available.
  • Thanks to vaccines, there has not been a single case of smallpox in the world since 1977.
  • The discovery and use of polio vaccines has all but eliminated polio in the Americas. In 1960, there were 2,525 cases of paralytic polio in the United States. By 1965, there were 61. Between 1980 and 1990, cases averaged 8 per year, and most of those were induced by vaccination! There has not been a single case of polio caused by the wild virus since 1979, with a rare case reported each year from persons coming into the country carrying the virus. In 1994, polio was declared eradicated in all of the Americas.
  • In 1988, the World Health Organization set a goal of eradication of poliomyelitis from the entire world by the end of year 2012. This is theoretically possible since the poliovirus is found only in humans, and humans can be immunized. Smallpox was the first disease in history to be eradicated. It seems likely that polio could follow in its footsteps.

The importance of keeping immunizations up-to-date

The danger is that disease outbreaks can still occur if there are groups of people who are not vaccinated. For example, between April and November 2007, the province of Quebec experienced two successive outbreaks in southeastern Quebec involving 95 individuals. More than 90% of the individuals affected were either unvaccinated or only partly vaccinated with a single dose of MMR vaccine.

In the United Kingdom, in 1974, the number of people who got the vaccine against pertussis (whooping cough) dropped. By 1978, the country had an epidemic of this disease. More than 100,000 people got the disease, and 36 people died.

In the early 1990's, a diphtheria epidemic occurred in the former Soviet Union after children stopped getting immunized and adults did not get booster shots. The number of cases of this epidemic soared from 839 in 1989 to nearly 50,000 in 1994. About 1,700 people died as a result of the epidemic.

Where can I get more information?

Your body makes antibodies in two ways: by getting the disease or by getting the vaccine. Getting the vaccine is a much safer way to make antibodies without having to suffer from the disease itself or the risk of becoming disabled or even dying.

After receiving a vaccine, the antibodies produced by your body stay with you for a long time. They remember how to fight off the germ. If the real germ that causes this disease (not the vaccine) enters your body in the future, your defence system knows how to fight it off.

Often, your immune system will remember how to fight a germ for the rest of your life. Sometimes, your immune system needs a reminder in the form of a booster shot to fight off this germ. For diseases, such as diphtheria and tetanus, you must take a booster shot every 10 years to remind your immune system of these diseases. So, stay safe and protected.

In some cases, for complete immunity, more than a single dose may be required. For example, the vaccine that protects against the bacterium Haemophilus influenzae serotype b (Hib), which causes meningitis. In other cases, a second or booster dose is needed to raise the immunity levels at a later age.

Some vaccines such as the flu shot (against influenza) require annual dosage for adults and children (older than 6 months) as the disease-causing viruses keep changing. New vaccines are needed every year to prepare your immune system to fight against new strain of viruses.

Herd immunity

Some vaccines also work by creating "herd immunity". When most people in a community have received a vaccine for a particular disease, the chance of an outbreak of that disease is greatly reduced. This "herd immunity" protects the small number of people who cannot be immunized for medical reasons or for whom the vaccine did not work. For herd immunity to be effective, however, as many people as possible must be vaccinated.

For more details, please see the chapters on specific vaccines in the Canadian Immunization Guide, Evergreen Edition.

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