Immunization: The most successful public health measure
In the last century, vaccines have saved more lives than any other health intervention. The World Health Organization estimates that every year, more than two million deaths are prevented worldwide due to immunization.
Immunization is an important, cost-effective and successful public health intervention. It effectively prevents disease, improves the health of Canadians, and reduces pressures on our health care system.
Vaccines have led to the eradication of smallpox, the near eradication of polio, and the control of other diseases, including polio and whooping cough, which once maimed or killed in large numbers. The risk of exposure to these and other vaccine preventable infections remains but immunization programs keep the risk of disease at bay. Still, for continued success of immunization programs, high levels of vaccine uptake among targeted populations are necessary. When immunization coverage rates drop significantly, disease returns.
The last major outbreak of measles in Canada affected about 200 people, most of who were not immunized against the disease. When a major drop in rates of immunization against whooping cough occurred in the UK in 1974, there was an outbreak of more than 100,000 cases and 36 deaths by 1978.
Vaccine coverage rates in Canada are high, but concerns expressed by some people about the safety of vaccines could lead to a drop in coverage rates. This would result in increases in preventable diseases such as poliomyelitis, measles, mumps, rubella, tetanus, diphtheria, pertussis, meningitis and hepatitis B.
While it is true that no vaccine is 100% safe or effective, serious adverse reactions are rare. The dangers of vaccine-preventable diseases are many times greater than the risks of a serious adverse reaction to the vaccine.
Canada has a rigorous scientific review and testing process for the quality, safety and efficacy of vaccines before they are approved for use. Following approval of a vaccine, a lot release program ensures that new lots of the vaccine retain the same characteristics as those used to first establish quality, safety and efficacy. Furthermore, the government monitors the effectiveness and safety of vaccines on an ongoing basis.
In addition, the Public Health Agency of Canada maintains a reporting system that health care providers use to report side-effects they feel may be caused by immunization. The rate of reported serious adverse events following immunization is very low -- between one and two for every one hundred thousand doses administered.
Allegations that vaccines can cause autism, multiple sclerosis, or macrophagic myofasciitis are not new and they have been taken seriously by the scientific and public health communities. There have been multiple scientific investigations into these alleged links over the last two decades, and the results have been reviewed by independent experts as well as public health and regulatory authorities. There is consensus that the evidence does not support any link between vaccines and these diseases.
There have been reports of links between thimerosal, a preservative used in some vaccines, and neuro-developmental disorders including autism. Several studies, using a variety of epidemiologic methods have produced consistent evidence that there is no association between thimerosal and autism. This finding was endorsed by Canada's National Advisory Committee on Immunization after scientific review in 2007. Scientific research in this area is ongoing and new studies continue to emerge which reject the link.
There is no legitimate safety reason to avoid the use of thimerosal-containing products for children or older individuals, including pregnant women. Nonetheless, because ongoing public concern about the safety of thimerosal could reduce immunization coverage rates, thimerosal is not used in most vaccines routinely used in Canada.
Canada's immunization program includes comprehensive safety measures, including:
- regulatory scrutiny before and after vaccines are approved for use
- ongoing monitoring for safety concerns
- rigorous scientific study of any alleged links between vaccines and serious adverse events, and
- independent expert review of the results of scientific studies.
As a result, the vaccines used in Canada are highly effective and safe.
Some individuals and organizations have concerns about "immunization overload" for babies and toddlers. These concerns are unfounded. The capacity of an infant's immune system is enormous and it is not compromised by vaccines scheduled in the first two years after birth. The recommended immunization schedule for infants in Canada is carefully timed to ensure that newborns and older babies get safe and effective protection from the diseases that are most likely to seriously harm them. Any delays in the start of immunization exposes children to unnecessary risks of illness.
Although immunization recommendations are made at the national level, immunization is not mandatory in Canada. Immunization programs are delivered by the provinces and the territories. Some provinces and territories may require that children receive certain vaccines before entering school, or that health care workers be immunized against some diseases. However, parents can decide to obtain a waiver for philosophical reasons. Also, those who refuse may be asked to stay away from school or work during an outbreak.
Studies around the world have repeatedly shown that immunization is a proven and effective public health measure, especially when weighed against the health risks from many serious vaccine-preventable illnesses.
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