Santé et Services sociaux Québec

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Frequently Asked Questions

Can you find accurate information about vaccination on the internet? PDF file.


Relevance of vaccination


Concern about the number of vaccines

Vaccination risks


How do vaccines work?

Vaccines protect us from diseases that can have serious consequences and even lead to death. They stimulate our body’s defense system, also called the immune system, to produce a way to protect us from infection (immunity) without causing disease.

Most vaccines contain a small amount of virus or attenuated (or dead) bacterium, or even a piece of a virus or bacterium. These vaccines stimulate the immune system, enabling it to produce antibodies that are stored in its memory for varying amounts of time, depending on the type of vaccine. The antibodies “remember” the previous tactics used to fight the virus or bacteria. If the virus or bacterium that actually causes the disease enters our body after vaccination, our immune system will know how to defend us.

For all sorts of reasons some people cannot be vaccinated. Others are not protected by the vaccine because it does not produce the desired effect in them. There are always some people who are not protected against disease. That’s why it’s important that as many people as possible get protected through vaccination. Indeed, by not catching the disease and transmitting it, people who have been vaccinated against disease protect people who are not.

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Can vaccines cause the diseases they are designed to fight?

Most vaccines contain a small amount of virus or attenuated (or dead) bacteria, or even a piece of a virus or bacteria. These vaccines stimulate the immune system, but they cannot cause the disease.

Vaccines enable the immune system to produce antibodies that will be stored in its memory for varying amounts of time, depending on the type of vaccine. The antibodies then “remember” the tactics used to fight against the virus or bacteria. If the virus or bacterium that actually causes the disease enters our body after vaccination, our immune system will know how to defend us.

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Are vaccines effective?

Yes, they are very effective. In fact, vaccines have eliminated smallpox worldwide. Polio has disappeared from Canada, while many diseases—such as diphtheria, tetanus, and German measles—are now rare here. The main cause of bacterial meningitis in children (Haemophilus influenzae type b) has also decreased significantly. Moreover, hepatitis B has practically disappeared among vaccinated young people.

For more information about vaccine effectiveness, refer to the table providing Canadian data about the results of certain vaccination programs. This table provides data about the number of cases of disease in Canada before and after the introduction of vaccination.

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Are vaccines safe?

Yes. In fact, they are very safe. Vaccines are produced according to very strict safety standards, but they can still have side effects.

Vaccination side effects are most often mild, such as a slight fever or tenderness at the injection site. These effects are temporary and part of the body's normal reaction to vaccines. In very rare instances, however, effects such as severe allergic reaction can occur after vaccination, such as after eating a new food. The person administering the vaccine can treat allergic reactions, should one occur. This is why it is recommended to wait for 15 minutes after being vaccinated.

Vaccine side effects are under constant surveillance in Quebec and around the world. Surveillance provides for screening for unexpected, severe, or rare effects, and intervening, if necessary. Through research, vaccines are also constantly being improved. For example, the pertussis (whooping-cough) vaccine used in the 1950s has been replaced with a vaccine that has many fewer side effects.

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Is vaccination mandatory in Québec?

No, but it is strongly recommended. Vaccination is the best protection against vaccine-preventable diseases. Getting vaccinated also helps prevent the spread of disease to people who cannot be vaccinated. Vaccination requires informed consent. Refusing vaccination must also be an informed decision.

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What goes into deciding to set up a vaccination program?

In Québec, the Ministère de la Santé et des Services sociaux determines which vaccines should be offered to the public based on recommendations by the Institut national en santé publique's Comité sur l’immunisation du Québec (CIQ). The committee and ministry base their determinations on many criteria, including:

  • The disease (the number of people who contract it, its severity, its consequences, its prevalence, groups affected, other means of prevention, etc.)
  • Vaccine accessibility
  • Public demands and clinical assessments by health-care professionals
  • Targeted objectives (the desire to control the disease more or less quickly)
  • Vaccine efficacy
  • Costs of vaccination compared to the medical and social costs associated with the disease and its complications
  • Availability of human and financial resources

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How is a vaccination schedule set up?

The vaccination schedule for a given vaccine is established based on the following principles:

  • The age groups to be vaccinated are those most at risk of contracting the disease.
  • The vaccine must be administered at the age when the disease is most likely to be contracted.
  • The vaccine must be effective at the age when it is administered.
  • The number of doses administered must result in short-term protection.
  • The need for and timing of booster doses must be assessed to achieve long-term protection.

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Why is Québec's vaccination schedule different from that of other Canadian provinces or other countries?

Because public-health officials can make different decisions depending on the criteria they use to determine which vaccines should be offered to the public. Public-health officials assess various criteria in making their determination, including:

  • Number of individuals who contract the disease (which can differ from one location to the next)
  • The disease (the number of people who contract it, its severity, its consequences, its prevalence, groups affected, other means of prevention, etc.)
  • Public demands and clinical assessments by health-care professionals
  • Targeted objectives (the desire to control the disease more or less quickly)
  • Costs of vaccination compared to the medical and social costs associated with the disease and its complications
  • Availability of human and financial resources

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Relevance of vaccination

Hadn't infectious diseases already begun to disappear before vaccines were introduced?

No. It is true that, prior to the advent of vaccines, infectious diseases were on the wane because of improved living conditions. They weren't, however, in the process of disappearing. With the use of vaccines, some infectious diseases have become rare and others have disappeared. For example, in recent years, the main cause of bacterial meningitis in children (Haemophilus influenzae type b) has decreased significantly. Yet living conditions have remained the same. So, only vaccination can account for the drop.

For more information about vaccination-program performance, refer to the table providing Canadian data about the results of certain vaccination programs. This table illustrates the effectiveness of vaccination programs by providing data about the number of cases of disease in Canada before and after the introduction of vaccination.

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What would happen if we stopped vaccinating?

Halting vaccination would cause infectious diseases to rapidly reappear and spread, which is what has happened in a number of countries. In Ireland, in particular, vaccination coverage for measles fell to 76% as the result of claims (which proved to be false) of a link between the vaccine and autism. The number of infected individuals with measles shot from 148 in 1999 to 1,603 in 2000, and 3 children died from measles-related complications.

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Why should we vaccinate against diseases that have been practically eliminated in our country?

Even if certain infectious diseases have become rare here, we still have vaccine-preventable diseases in Canada. In particular, tetanus will always be around, because it is caused by a bacterium that lives in the soil. Moreover, vaccine-preventable diseases occur very frequently in many countries. They can be caught when traveling or be brought here by people coming from these countries. Continuing to protect against them is therefore still important.

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Why should I have my child vaccinated if most other people are vaccinated and cannot pass on the disease?

Because unvaccinated children are at greater risk than anyone of contracting a contagious disease, even in countries where very many people have been vaccinated. For example, it has been shown in the United States that unvaccinated children have 22 to 35 times the risk of contracting measles and 6 times the risk of contracting whooping cough than vaccinated children. Moreover, unvaccinated children may transmit contagious diseases to children who cannot receive the vaccine or to those who have only partial immunity, especially infants..

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Why should I have my child vaccinated against diseases that appear harmless, like chickenpox?

Because chickenpox can have severe consequences. Prior to implementation of the chickenpox vaccination program, hundreds of children in Québec were hospitalized each year because of related complications. Some of these complications can even cause death.

In particular, chickenpox can cause skin infections, ear infections, pneumonia, and blood infections. Chickenpox substantially increases the risk of a serious streptococcal infection, including flesh-eating bacteria.

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Aren't vaccines just a way for pharmaceutical companies to get rich?

Vaccines are indispensable and unavoidable in improving public health. Regardless of whether manufacturing them is profitable or not for pharmaceutical companies, the health impacts should production stop would be unacceptable.

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Don't natural infections provide better protection than vaccines?

While it is true that, in most cases, a natural infection provides better protection than vaccines, but at what a cost! Vaccine-preventable diseases involve suffering, complications, sequelae, and possibly even death. Natural protection involves much more risk than vaccines and their side effects. Vaccines also have the advantage of sometimes being able to protect against several strains of the disease. When someone contracts a disease, they only contract one strain at a time. As a result, natural infection only provides protection against the particular strain.

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Do the risks associated with the actual disease outweigh the possible side effects of vaccination?

Yes, in every case the serious risks associated with vaccines are much rarer than those associated with the disease.

For more information, consult the summary table comparing disease symptoms, their duration, possible complications, and possible reactions to vaccines.

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Are there alternatives to vaccination (e.g. breast-feeding, healthy diet, and homeopathy)?

No. Besides infection, only a vaccine can stimulate the body to produce specific antibodies against a virus or bacterium.

A healthy diet helps keep the body's overall defense mechanisms in good working order. It helps fight infections but can't prevent them.

Breast-feeding provides a certain level of protection against various infections such as colds, ear infections, and diarrhea. Yet it only provides infants with partial and short-lived protection against diseases that vaccination can prevent.

Medicinal herbs, homeopathy, and vitamins are no substitutes for vaccines.

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Why do we need vaccination if we have the best hygiene and health conditions here in Canada?

Because improving living conditions reduces the risks of infection and transmission, but doesn't eliminate them. Many countries with living conditions similar to ours have experienced a substantial increase in vaccine-preventable diseases when the number of vaccinated people dropped. 

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Concern about the number of vaccines

Can vaccines run down or overload the immune system?

No. Vaccines represent only a very small fraction of the antigens against which the immune system must defend itself naturally every day. Moreover, vaccines use only an infinitesimally small part of immune memory.

From birth, the human body naturally defends itself against thousands of antigens found in water, in the air, in food, and on items on a daily basis. Upon entering the body, these antigens trigger the immune system to react. The immune system begins producing specific antibodies against the antigen and commits its reaction to memory to recognize and eliminate it in the future.

Scientists estimate that an infant's immune system can react to 10,000 different antigens at a time and that it could eventually recognize and react to hundreds of thousands, even millions of different microorganisms.

Vaccines for children and adults use only and infinitesimally small part of immune memory. Moreover, even if children receive more vaccines than in the past, the total amount of antigens in today's vaccines is now much lower. For example, the 4 vaccines on the 1980 regular vaccination schedule contained a total of about 3041 antigens. In 2000, the 11 vaccines on the regular calendar had only 126.

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Is there a maximum number of vaccinations that a child can receive in a single visit?

No, there is no real maximum number of vaccines that a child can get at any one time. Giving a child several vaccines simultaneously provides earlier protection for a larger number of diseases. In addition, it saves parents money and time related to repeated visits. Only vaccines that are harmless and effective when administered at the same time are given under those conditions.

Furthermore, giving several injections during the same visit does not increase the frequency, intensity, or severity of side effects. In addition, the treatment for the child's discomfort will be the same in the case of one or several injections. Of course, whenever possible, vaccines combining several diseases (e.g. DTaP–Polio–Hib which protects against diphtheria, whooping cough (pertussis), tetanus, polio, and Haemophilus influenzae type b infections) should be preferred over those for just one. Combination vaccines reduce the number of injections and child discomfort.

Moreover, research is ongoing into other safe, effective administration methods, such as orally and nasal spray. After all, the goal is protection, not unnecessary suffering.

For more information about multiple injections, refer to the pamphlet Multiple Injections—More than one injection: more than one advantage! This link open a new window..

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My child is so little. Can't I put off his vaccinations until after his first birthday?

No, because the risk of contracting many diseases is higher in the first year of life (e.g. meningitis caused by Haemophilus influenzae type b, pertussis, pneumococcal infection).

Following the Ministère de la Santé et des Services sociaux’s recommended schedule for your child provides protection when he or she needs it most. Even if you don't like the idea of your child getting a shot, keep in mind that it can spare him or her much more discomfort and possibly complications.

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Vaccination risks

Is it true that vaccines can cause serious illness?

 In reality, vaccines are among modern medicine's safest tools. However, they make easy targets for those wanting to explain the occurrence of a disease or health problem. This can be attributed to the following:

  • A vaccine is a product administered to a healthy person, often a toddler, to prevent but not treat a disease. For this reason parents have little tolerance for the occasional side effects their children experience.
  • A number of diseases or syndromes naturally occur around the same age when children receive various vaccines. The appearance of these diseases in that period is merely a coincidence. The fact that parents see a causal relationship with vaccination is quite understandable because often the medical profession cannot explain many of these diseases.

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Should I be afraid of post-vaccination side effects such as fever, pain, or other possible reactions?

Like many medications, vaccines can sometimes cause side effects—most of them minor. For example, many people experience soreness at the injection site, while others feel sick or develop a mild or moderate fever. These effects are temporary and are normal reactions to the vaccine’s agent. On the other hand, in very rare cases, severe allergic reactions can arise after vaccination—like what can happen when someone eats a new food they are allergic to. These severe allergic reactions can be treated on site by the person administering the vaccine.

In Québec, a monitoring system has been put in place to detect serious reactions associated with vaccines, whether rare or unexpected.

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How to tell fact from fiction?

To establish a causal relationship between a vaccine and a disease, scientists must rigorously study various criteria. They must consider the relationship in time (the vaccine preceded the disease). This relationship is essential but not sufficient; otherwise scientists would often draw incorrect conclusions.

For example, the fact that a child’s first teeth appear at the same time as the administration of the third vaccine dose against diphtheria, tetanus, pertussis, polio, and severe Hib infections (DTaP-Polio-Hib) does not mean the vaccine made the teeth come in. Similarly, the fact that children begin to walk shortly after receiving the vaccine against measles, mumps, and rubella (MMR) does not mean the vaccine caused them to walk.

It’s also important scientists check if the problem is more common among vaccinated than non-vaccinated individuals. Each study's findings must be confirmed by other studies elsewhere in the world.

Scientific studies around the world on the risks associated with vaccination demonstrate the following:

  • The MMR (measles, mumps, and rubella) vaccine does not cause autism or inflammatory bowel disease.
  • Thimerosal (a preservative) does not cause autism.
  • The pertussis vaccine does not cause brain damage.
  • The hepatitis B vaccine does not cause multiple sclerosis (MS) or relapse in people with MS and does not cause chronic fatigue syndrome.
  • Childhood vaccines do not increase the risk of asthma or allergies.
  • Vaccines do not cause sudden infant death syndrome.
  • Vaccines do not cause cancer or Type 1 diabetes.
  • Influenza (flu) vaccines do not cause Bell's palsy (facial paralysis).

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Can the measles, mumps, and rubella (MMR) vaccine cause autism or other developmental disorders?

No. In fact, many studies conducted in the United States, the United Kingdom, Denmark, and Québec involving hundreds of thousands of children have proven that it doesn't.

The reason why autism is often mistakenly associated with the MMR vaccine is that it is administered around the same age that the disease is diagnosed. Autism is usually diagnosed at age 18 to 30 months, while children receive the MMR vaccine at age 12 to 18 months.

Since the 1990s, the autism rate has also increased in quite a few countries. The increase, however, cannot be attributed to the MMR vaccine, but rather to the fact that pervasive developmental disorders are now considered a form of autism. Health-care professionals are now more aware of autism and diagnose it more often.

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Can the thimerosal used in vaccines cause autism or other developmental disorders?

No. Thimerosal does not cause autism or other developmental disorders.

Thimerosal, a mercury derivative used as a preservative in certain vaccines, is not harmful.

The form of mercury that can produce severe brain and nerve lesions if ingested in large quantities is methylmercury. Once within the body, thimerosal is converted into another product, called ethylmercury. Unlike methylmercury, ethylmercury is rapidly eliminated from the body and the risk of it accumulating is low.

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Is the aluminum found in certain vaccines toxic?

While vaccines can contain aluminum salts, the quantity of aluminum in a given vaccine is less than 1 mg per dose. Based on observations, this amount is not harmful to humans. Much larger amounts of aluminum salts are ingested and absorbed by the body when a person takes an antacid (for example, 200 to 400 mg of aluminum hydroxide per tablet) without causing appreciable side effects.

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Can vaccines transmit animal diseases to humans?

Since vaccines are biological products, sometimes animal cells must be used in producing them. This process is subject to strict regulation so that the vaccines produced entail no risk to human safety. During the manufacturing process, the vaccines are purified and all animal cells are eliminated. Moreover, each vaccine lot undergoes testing to ensure that it contains no infectious agents.

Bovine serum is sometimes used in producing some vaccines in Canada. Researchers in a number of countries have studied the risk of exposure to mad-cow disease through vaccination. The risk has been determined to be 1 out of 40 billion doses. Despite this extremely low risk, vaccine manufacturers are striving to find components to replace bovine serum.

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Are we able to detect unexpected side effects?

Yes, as a result of the surveillance systems designed to detect both rare and serious unexpected effects.

In Québec, physicians and nurses must declare any unusual effects occurring after vaccination to public-health authorities. Québec's program is related to the Public Health Agency of Canada's national program and the World Health Organization's international program.

Screening for unusual side effects leads to more specific research on these phenomena and to the adoption of appropriate measures. Here are some recent examples:

  • Ocular respiratory syndrome and the influenza vaccine: Detection of this for the first time in Quebec in 2000, at a frequency of 46.6 cases per 100,000 doses, led to modifications in the vaccine's manufacturing process to reduce the risk of this syndrome.
  • Meningitis and Trivirix vaccine (against measles, mumps, and rubella): Its detection in Canada 1988, at a frequency of 1 case for 62,000 doses, resulted in the vaccine being withdrawn from the market.

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What is the Vaccine Injury Compensation Program?

Despite vaccines being highly safe, some adverse reactions can occur in extremely rare instances. The Gouvernement du Québec initiated the provincial compensation program for vaccination victims in 1985 under the Public Health Act. The program entitles victims of bodily injury as the result of vaccination to compensation from the Minister of Health and Social Services. Québec is the only province to have implemented such a program.

The Public Health Act defines victim as: "the vaccinated person, a person having contracted the disease from a vaccinated person, the foetus of either of such persons or, if a death occurs, the person who is entitled to a death benefit." The Act defines bodily injury as: "any serious permanent physical or mental injury, or death."

The main points in the compensation program are as follows:

  • The vaccination must have taken place in Québec.
  • The targeted products are vaccines or immunoglobulins for diseases or infections established by regulation.
  • Compensation is awarded on a no-fault basis.

For more information, refer to the section on Compensation.

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