Immunization is one of the greatest public health achievements of the 20th century. Free, universal vaccination programs in Canada have saved millions of children from death or disability from communicable diseases.

Smallpox and polio
The global eradication of smallpox is one of the most remarkable results of immunization. This disease infected approximately 20 million people worldwide in 1966. Thanks to vaccination, the smallpox has been declared eradicated in 1980 by the World Health Organization. Poliomyelitis (Polio) has virtually disappeared from North America and is the next target for global eradication.

Pertussis, diphtheria, measles, hib meningitis
With the use of modern vaccines, most Canadian families and health care professionals have never experienced the devastating effects of once common childhood diseases. Vaccination has dramatically reduced the number of annual cases of pertussis, diphtheria, measles and hib meningitis in Canada. In countries where vaccination coverage has fallen, outbreaks of disease have returned leading to avoidable illness and death. Recent outbreaks of whooping cough in Great Britain and diphtheria in Russia are just two examples.

Prior to the availability of the measles vaccine, most Canadians were exposed to measles during their lifetime. On average, 80,000 cases were reported annually. During epidemics, which occurred every two to three years, this number was a high as 300,000 cases per year. In Canada, there were between 50-75 deaths each year due to measles.

Since the implementation of the two-dose vaccination programs against measles in 1995, the number of annual cases has dropped significantly. In 1999, only 29 cases were reported in Canada overall. From individuals who receive only one dose of measles vaccine, it is estimated that 10 per cent of them may not develop adequate immunity. Both doses are required for optimal protection against this disease and are legally required for school attendance in Ontario.