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• Ages and Stages
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Immunization is one of the most important ways to keep your child healthy. Before many of today’s vaccines were available, children often got very sick or even died from diseases that can now be prevented.

Vaccines are very safe. There are rarely reasons not to get vaccinated.

Who ensures that vaccines are safe?

Like all medicines, vaccines must go through a series of steps before they are approved for use. Vaccines must be shown to be safe and effective in preventing the diseases they target.

Once a vaccine is in use, health authorities continue to ensure that it is safe. One way is through a unique program called IMPACT (Immunization Monitoring Program, ACTive). Nurses at 12 children’s hospitals across Canada review all hospital admissions for certain serious illnesses, and then collect information to determine whether the illness happened after vaccination.

Canada also has a system where any doctor or nurse can fill out a report to Health Canada if they have a patient with a serious health problem that occurred after vaccination.

Are there side effects to vaccines?

After a vaccine, some children may have a fever or may feel pain where the needle went into the arm or leg. If necessary, taking acetaminophen can help ease the pain.

Other side effects are very rare. The chance of getting sick from the disease far outweighs the very small risk of reacting to an immunization.

Is it better to give vaccines one at a time or combined with others?

Many of the shots your child will receive have several vaccines in them, such as the 5-in-1 vaccine (which protects against diphtheria, polio, tetanus, pertussis and Haemophilus influenzae type B or Hib disease) and the MMR vaccine (which protects against measles, mumps and rubella). 

A number of studies have shown that giving combinations of vaccines is both safe and effective and does not increase side effects. It’s also practical, allowing your child to receive several vaccinations during the same visit. This means fewer office visits, saving you both time and money. Fewer shots may also be less traumatic for your child.

Is it safer to wait until my baby is older to start vaccination?

The reason that vaccination starts at 2 months of age is to protect babies against pertussis and Hib disease as early in life as possible, since these diseases are more harmful to young babies.

There is no evidence that side effects from vaccination are more common in younger infants. 

Can measles or MMR vaccine cause autism or other developmental disorders? 

No. There is NO scientific evidence to support this theory. 

All the research on the MMR vaccine and autism has been reviewed independently by expert committees who agree that there is no scientific evidence that MMR causes autism, autistic spectrum disorders or inflammatory bowel disease. 

Can mercury in vaccines cause brain damage, retardation, autism, attention deficit disorder, learning disorders? 

In the past, mercury was present in some vaccines in the form of thimerosal. Thimerosal is an organic mercury compound that has been used as a preservative in some vaccines and other medications since the 1930s. 

There is no evidence that the presence of thimerosal in vaccines causes brain damage in children. Large studies in which some children received vaccines containing thimerosal and received thimerosal-free vaccines showed no difference in the number of children who developed autism. 

As of March 2001, all vaccines for routine immunization of children in Canada and the United States are produced without thimerosal. Thimerosal is a preservative used in the production of vaccines that are stored in vials (containers) that have more than one dose. These are the vaccines used for mass immunization programs, such as influenza (given annually at a specific time of year to many Canadians). While the influenza vaccine is made in single-vial units as well-without thimerosal-it may not be available in all provinces and territories.

Can immunization cause SIDS? 

Several large studies have found that there is no association between vaccination and SIDS (sudden infant death syndrome). In fact, all of the studies found that babies who died of SIDS were less likely to have been vaccinated recently than were babies in the control group (babies chosen to match the babies who died of SIDS, according to factors such as age, sex and weight to make comparisons). 

Can vaccines cause asthma and other kinds of allergic disease? 

Recent studies have shown that immunization does not increase the frequency of asthma and other allergic diseases in children. 

Where can I get more information?

• Talk to your doctor or public health nurse if you have questions about vaccines or your child’s health.
• The CPS has also published a book for parents called Your Child’s Best Shot: A Parent’s Guide to Vaccination. 

Reviewed by the following CPS Committees:
Infectious Diseases and Immunization Committee

Last updated: August 2008