Thanks to vaccination, fewer people suffer from vaccine-preventable diseases, and the effects of such diseases are rarer in the general population. Consequently, the benefits of vaccination are less apparent than the risks. Vaccination has therefore fallen victim to its success.

The risks associated with vaccines, whether real or perceived, are of concern to a lot of people. In fact, many people worry more about risks associated to vaccines than risks associated to diseases that vaccines help prevent. However, research has shown that serious risks associated with vaccines are much rarer than those related to diseases.

Some media and websites have helped create and maintain public anxiety regarding vaccination. Here are some scientifically proven facts to help clarify certain views about vaccination.

Vaccines usually do not cause serious illness

Vaccines are among the safest tools of modern medicine. Safety standards for vaccines are extremely strict. Research has also proven that serious risks associated with vaccines are much rarer than those related to diseases against which they protect.

However, vaccines are easy targets for people who seek to explain the emergence of a disease or health problem.

In Québec, a surveillance program allows for the detection of serious, rare or unexpected reactions that could be associated to vaccines. When such reactions occur, scientists are informed and must examine several criteria rigorously.

In particular, scientists must take into account time elapsed between the person receiving the vaccine and onset of symptoms of the illness presented. Time elapsed is an essential element but not the only criterion considered. For example, young children receive their 3rd dose of the DTaP-IPV-Hib Vaccine against diphtheria, whooping cough, tetanus, polio and serious Hib infections at around 6 months of age. Often, their first teeth appear at the same time. The fact that these two events occur at the same time does not mean the vaccine causes teething.

Scientists must also analyse other criteria in order to avoid reaching a wrong conclusion. They must continue their analysis by checking whether the reported problem is more common in those vaccinated than in those who are not. Furthermore, they must ensure that their conclusions are in line with those of other studies elsewhere in the world.

For example, scientific work conducted on a global scale on risks associated with vaccines clearly shows that:

  • The MMR Vaccine against measles, mumps and rubella does not cause autism or inflammatory bowel diseases
  • Thimerosal does not cause autism
  • The vaccine against whooping cough does not cause brain damage
  • The vaccine against hepatitis B does not cause multiple sclerosis or relapses in people with this disease. It does not cause chronic fatigue syndrome either
  • Vaccines given to children do not increase risk of asthma or allergies
  • Vaccines do not cause sudden infant death syndrome
  • Vaccines do not cause cancer or type 1 diabetes
  • Vaccines against the flu do not cause Bell's palsy (facial paralysis)

In Québec, anyone who believes they have been injured by a vaccine can file a claim for compensation with the Ministère de la Santé et des Services sociaux. To find out more, consult the Vaccine Injury Compensation Program page.

Can vaccines cause the disease they protect against?

Most vaccines are inactivated.

Inactivated vaccines contain only pieces of bacteria or “killed” viruses. These vaccines stimulate the immune system of the person who is given the vaccine but cannot cause the disease.

Some vaccines are live.

Live vaccines contain a small amount of attenuated bacteria or viruses. During production, they are weakened so that they are incapable of transmitting disease. Like inactivated vaccines, live vaccines stimulate the immune system of the person who is given the vaccine. This means that a live vaccine is very unlikely to cause disease.

However, in a very small number of people, this type of vaccine may cause a mild form of the disease it protects against. For example, a child who is given the chickenpox vaccine might develop a few spots that look like chickenpox. They are very rarely contagious and clear up quickly. The mild form of a disease is not dangerous and shows that the vaccine is effective.

Furthermore, live vaccines should not be given to people who have a weakened immune system because of the risk of the vaccine causing a severe form of the disease.

In Québec, most vaccines given under the Québec Immunization Program are inactivated. Only the following vaccines are live: the combined measles, mumps and rubella vaccine (MMR), the combined measles, mumps, rubella and chicken pox (varicella) vaccine (MMR-Var), the chicken pox (varicella) vaccine, the rotavirus vaccine and the intranasal flu vaccine.

To learn more, read How Vaccines Work.

Vaccines do not spread animal diseases to humans

Given that vaccines are biological products, it is necessary to sometimes use animal cells in their production. This procedure is subject to strict regulations such that the vaccines present no risk to human health. During production, the vaccines are purified and rid of all animal cells. In addition, each batch of vaccines is tested to ensure it contains no infectious agent.

Vaccines cannot exhaust or overload the immune system

Scientists estimate that an infant’s immune system can react to 10,000 different microbes simultaneously. It is also able to recognise thousands, or even millions of different microbes and to react to them with no problem.

In addition, even if children receive more vaccines than before, their total content of weakened microbes or parts of microbes is much less. For example, in 1980, the four vaccines in the regular immunisation schedule contained a total of 3,041 weakened microbes or parts of microbes. In 2000, the 11 vaccines in the regular schedule only contain a total of 126.

To learn more about how vaccines protect us by stimulating our immune system, read How Vaccines Work on the Vaccination page.

Several vaccines can be safely administered in a single appointment

There is no limit to the number of vaccines a person can receive in one shot. The administration of several vaccines at one time, referred to as ‘multiple injections’, has many benefits. To learn more, read Benefits of Multiple Injections on the Vaccination for Children page.

A healthy diet, breastfeeding or homeopathy cannot replace vaccination

Besides the disease itself, only a vaccine can stimulate the production of specific antibodies against the virus or bacterium responsible for that particular disease.

A healthy diet helps fight infections and illnesses but does not prevent them. Eating well only contributes to the proper functioning of the general mechanisms of the body's defense.

Breastfeeding provides some protection against many infections, including colds and ear infections.

However, breastfed infants are protected against certain vaccine-preventable diseases only partially and for a short time.

Also, medicinal herbs, homeopathy and vitamins do not replace vaccines.

Relying on the natural protection given by catching a disease is much more risky than getting vaccinated against that particular disease

In most cases, catching an infection naturally protects better than a vaccine against that particular infection. However, relying on this natural protection entails considerably greater risk than vaccines and reactions they may cause. Indeed, vaccine-preventable diseases are accompanied by pain and complications. They may also lead to serious complications and even death. In all cases, serious risks associated with vaccines are much less frequent than those related to disease.

Some diseases can be caused by different types of microbes, or ‘strains’. When a disease is caught, only a single strain is contracted at a time. Therefore, natural protection is only valid for that particular strain. Some vaccines have the benefit of protecting against several strains of a disease.

Chickenpox can have serious consequences

Chickenpox can have serious consequences. Some complications of this disease can lead to death. Before establishment of the chickenpox vaccination program, hundreds of children were hospitalised each year in Québec due to complications of this disease.

Infections of the skin, blood and ears, as well as pneumonia, are all complications of chickenpox. This disease greatly increases the risk of getting a serious infection caused by streptococcus, including disease caused by flesh-eating bacteria.

Thimerosal does not cause autism or other developmental disorders

The flu vaccine contains a preservative called thimerosal. Thimerosal is a derivative of mercury that is not dangerous.

Once in the body, it is metabolised to ethylmercury. The form of mercury that can cause serious brain and nerve damage if consumed in large quantities is called methylmercury. Contrary to methylmercury, the body gets rid of ethylmercury very quickly and there is little risk of it accumulating.

Aluminum salts contained in some vaccines are not toxic

Vaccines may contain aluminum salts, but the amount of aluminum is less than 1 mg per dose of vaccine, a quantity that can cause no harm to a person. When someone takes antacids, for example, their body absorbs a significantly higher quantity of aluminum salts without causing any side effects.

Vaccines are still necessary in Canada, even if hygiene and sanitary conditions are good

Improving living conditions reduces the risk of infection and disease transmission, but does not eradicate them.

In many countries with living conditions similar to ours, vaccine-preventable diseases make a strong comeback when the number of people vaccinated drops. Even in a country such as Canada, 1 person in 3,000 still dies today as a result of measles.

Infectious diseases were not already in the process of disappearing before the advent of vaccines

Before the advent of vaccines, infectious diseases had started to decrease due to the improvement of living conditions. However, they were not disappearing. It is with vaccines that some infectious diseases have become rare and others have disappeared. For example, the biggest cause of bacterial meningitis in children is the bacterium Haemophilus influenzae type b. Over the last few years, this bacterium has decreased significantly in countries that offer the vaccine against the infection. However, conditions of life have remained the same. Vaccination is the only explanation for the decrease.

How to Recognise a Good Source of Information

There are many sources of information on vaccination: websites, television shows, magazines, social media such as Facebook, etc.

However, credible sources of information are sometimes lost in a flurry of sources that are not founded on any recognised scientific ground and may even contain misleading information.

You can find trustworthy information on vaccination by keeping in mind that a reliable source does the following:

  • Clearly articulates its mission and purpose
  • Offers current information based upon serious scientific data and approved by recognised organisations and experts
  • Indicates groups or organisations financing them, as well as their contact information where applicable

Here are a few questions to ask yourself in determining the reliability of a source of information:

  • What is the mission and purpose of the source of information?
    • Does it aim to inform the public?
    • Does it support a personal cause or a specific group?
    • Is it selling products or documents?
  • What is the basis of the information given?
    • Is it personal testimonials or opinions?
    • Is the information based on serious scientific data approved by recognised organisations in the field?
  • What is the source of information’s competency in health issues?
    • Is it someone with recognised medical training?
    • Is it a health organisation renowned in the field of vaccination?
    • Is the person a member of recognised associations of public health professionals, doctors, nurses or scientists?
      Some writers are merely presented as eminent ‘specialists’, internationally recognised researchers or renowned scientists. If there is no further mention of their training or their membership to a recognised organisation, be wary of the information
  • Is the information current?
    • Does it refer to current data?