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Vaccine safety
Do vaccines cause side effects?
Vaccines, like any medicine or supplement (including vitamins), may cause some side effects. Vaccine side effects are generally mild, like soreness, redness, and swelling where the vaccine was given, or fever, and usually last 1 to 2 days. Serious side effects are very rare. The dangers of vaccine-preventable diseases are many times greater than the risks of a serious vaccine side effect.
How long does it take for a vaccine to be tested and approved for use in Canada?
It can take up to ten years or longer for a vaccine to be developed, tested, and approved by Health Canada. Occasionally, the process can be expedited (happen more quickly) if a vaccine is urgently needed (for example, during a pandemic). No safety steps are skipped in these cases, and the vaccine must meet all the same safety requirements. An example is the COVID-19 vaccines.
- Vaccines are among the most strictly regulated medical products in Canada.
- All vaccines undergo an in-depth testing process and must be shown to be safe and effective before being approved for use in Canada.
- This process goes through several phases to gather all the scientific information necessary to ensure the safety and efficacy of the vaccine.
- Once a vaccine has been approved for use, and for as long as the vaccine is used, its safety is continuously monitored.
- Canada has one of the best vaccine safety programs in the world.
How do we know vaccines are safe?
Only vaccines that are proven safe, effective, and of high quality are approved for use in Canada.
Here are some important things to know about vaccine safety:
- The vaccine approval process is more stringent than most drugs available in Canada.
- It can take up to ten years or longer for a vaccine to be developed, tested, and approved by Health Canada. Occasionally, the process can be expedited (happen more quickly) if a vaccine is urgently needed (for example, during a pandemic). No safety steps are skipped in these cases, and the vaccine must meet all the same safety requirements. An example is COVID-19 vaccines.
- Health Canada only approves a vaccine if it is safe, works, meets manufacturing standards, and the benefits outweigh the risks.
- Because vaccines are given to healthy people, including children, they are held to the highest safety standard—even higher than most drugs used for treatment.
- Like any medicine or supplement (including vitamins), vaccines can cause side effects. Usually vaccine side effects are minor, such as a sore arm or mild fever, and go away quickly. Many people who receive vaccines have no side effects at all. Serious side effects are very rare.
- A vaccine’s safety is continuously monitored following its approval.
- Canada has several advanced systems in place (at the local, provincial, and national levels) to carefully monitor the safety of vaccines and detect any safety concerns.
- In the rare event that a lot (batch) of vaccines result in an unexpected side effect, these systems can ensure that the rest is not used.
I have a chronic disease. Is it safe for me to get vaccinated?
Many people living with chronic diseases can safely receive routine vaccines. Chronic diseases may increase a person's risk of infection or their risk of more severe disease should infection occur; this makes getting vaccinated especially important.
There may be different vaccine schedules or recommendations for people living with certain chronic diseases. Your healthcare provider (medical specialist, doctor, or public health nurse) can tell you which vaccines are recommended for you.
Examples of chronic diseases include asplenia or hyposplenia, chronic renal disease, neurologic disorder, chronic lung, heart, and liver disease, endocrine and metabolic diseases, non-malignancy hematologic disorders, autoimmune conditions, cancer, and chronic salicylate therapy in children.
Tell your healthcare provider if you are living with a chronic disease.
Is it safe for my child to get more than one vaccine at the same time?
Getting multiple vaccines at the same visit is safe and ensures your child is protected as quickly as possible during their early years of life when they are most at risk. Getting several vaccines at the same time also means fewer appointments and periods of pain and discomfort for your child, which may reduce your child’s risk of developing needle fears.
Research shows that routine childhood vaccines work just as well when they are given at the same visit as when they are given at separate visits.
Can getting multiple vaccines at the same time overwhelm my baby's immune system?
No. Getting multiple vaccines at the same visit will not overwhelm your baby’s immune system. It’s safe, and makes sure your baby is protected sooner rather than later.
- Every day, a healthy infant’s immune system successfully fights off millions of germs (antigens) they come across in their surroundings.
- Vaccines contain only a tiny fraction of the antigens (germs) that infants come across every day.
- Infants are born with thousands of antibodies that provide protection. They are ready to fight against many different diseases. They are also born with the immune cells that are needed to make antibodies in response to getting many vaccines at one time.
- Theoretically, infants have the capacity to produce one billion antibodies. So, it is estimated that they could handle up to 10,000 vaccines at any one time.
- Vaccines do not overwhelm or weaken a child’s immune system. Instead, they make it stronger by providing protection against diseases.
- Even combination vaccines, which protect against multiple diseases, are easy for your child’s immune system to handle.
As one doctor put it, “Worrying about too many vaccines is like worrying about a thimble of water getting you wet when you are swimming in an ocean.”
Listen to Dr. Paul Offit MD, talk about whether babies get too many vaccines.
Are combination vaccines safe?
Yes, combination vaccines are safe.
- Combination vaccines take two or more vaccines that could be given by themselves and put them into a single injection so that children can get protection against several diseases with just one shot.
- The diphtheria, tetanus, pertussis, hepatitis B, polio, haemophilus influenzae type b (DTaP-HB-IPV-Hib) vaccineand measles, mumps, rubella (MMR) vaccine are examples of combination vaccines.
- Before a new combination vaccine is approved, it must be shown to be as effective as each vaccine given separately.
- The side effects of combination vaccines are similar to those of the individual vaccines given separately.
- Most of the vaccines available in combinations are not available separately. If one component of a vaccine is declined, all other components are also declined. For instance, refusing the measles vaccine means that a child cannot be vaccinated against rubella and mumps, either, because the measles vaccine in Canada is only available in combination with the mumps and rubella vaccines.
My child accidentally got an extra dose of vaccine. Is this harmful?
Getting an extra dose of the routine childhood vaccines is not harmful. Extra doses are often given when a person’s vaccination history is unknown.
Is it safe to repeat vaccines? I can’t find my immunization record.
Without an immunization record (or proof of immunity to a disease), a person is considered unimmunized and unprotected and should generally be vaccinated (or revaccinated) to ensure protection. It is safe to repeat vaccines.
Can a vaccine give me or my child the disease it’s supposed to prevent?
It isn’t possible for inactivated (killed) vaccines to cause disease. This is because a germ has to be alive to cause disease.
Some vaccines contain weakened live versions of the whole germ, such as Measles, Mumps, Rubella (MMR) vaccine, and chickenpox (varicella) vaccine. These weakened germs in live vaccines will not cause the disease in a person with a healthy immune system. However, live vaccines are not given to people with very weak immune systems as they may develop the disease the vaccine is meant to protect against. Your health care provider will make sure that you or your child can safely receive a live vaccine before giving it.
Where can I find information on vaccine side effects?
You can find general information on vaccine side effects on:
You can find information on side effects of specific vaccines in:
- The vaccine HealthLinkBC Files, which are linked to in BC’s routine immunization schedules.
- Our Vaccines section.
- The Canadian Immunization Guide’s active vaccines sections.
During the vaccination appointment, your health care provider will review the vaccine side effects and will advise that you seek medical attention if you or your child experiences a serious or unexpected reaction.
Do vaccines cause chronic illness or other long-term health problems?
- There is no evidence that vaccines cause health problems such as autism, asthma, SIDS, or autoimmune diseases such as diabetes and multiple sclerosis.
- We learn about a vaccine’s safety during clinical trials before it is approved and monitor it’s safety continually as millions of doses are administered after its approval.
- We’ve been monitoring the safety of vaccines for more than 50 years and we can say that the chance a vaccine will cause unexpected long-term health problems is extremely low.
Can vaccines cause autism?
- Many large studies have found that vaccines do NOT cause autism.
- A number of credible studies have compared the health of vaccinated and unvaccinated children over many years. They have found that unvaccinated children were just as likely to develop autism as vaccinated children.
- It is not known exactly why some children develop autism; current research suggests that both genetics and environment likely play a role.
- Because children with autism are often diagnosed after the age when they receive some vaccines, this has led some people to think that vaccines cause autism. But just because one thing happens after another, it does not mean there is a link between them.
- Much of the controversy around a possible link between the MMR vaccine and autism came from a single small study published in 1998.
- The study was found to be fraudulent and was withdrawn by the journal that published it.
- Many large, high-quality scientific studies around the world have since taken place and have found no link between the MMR vaccine and autism. A summary of several of these studies and their conclusions are available.
Can vaccines cause SIDS?
Vaccines have not been shown to cause sudden infant death syndrome (SIDS). Infants receive multiple vaccines between two and four months of age. This period is also when the risk of SIDS is highest. This has led some people to question if the two are related. However, because the incidence of SIDS is the same in children who do or do not receive vaccines, we know that SIDS is not caused by vaccines.
An example of how the hepatitis B vaccine was shown to not cause SIDS:
- In 1999, a news program in the US aired a story claiming that the hepatitis B vaccine caused SIDS.
- At the time of the introduction of the hepatitis B vaccine for routine use in all infants, about 5,000 children died every year from SIDS.
- Within 10 years of the introduction of the hepatitis B vaccine the use of the vaccine increased to about 90 percent of all infants receiving hepatitis B vaccine and the incidence of SIDS in that age group decreased dramatically to about 1,600 cases each year.
- The cause of the decrease in SIDS cases was attributed to the introduction of the “Back to Sleep” program by the American Academy of Pediatrics (AAP).
- However, since immunizations are given to about 90 percent of children less than 1 year of age, and about 1,600 cases of SIDS occur every year, it would be expected, statistically, that every year about 50 cases of SIDS will occur within 24 hours of receipt of a vaccine.
Multiple research studies and safety reviews have looked at possible links between vaccines and SIDS. The evidence added up over many years does not show any links between childhood immunization and SIDS. Some studies have found that infants who died of SIDS were less likely to have been immunized.
Do vaccines cause asthma and allergic diseases?
Several large studies have looked at the risk of developing asthma following receipt of a number of different childhood vaccines. Vaccines were not shown to cause asthma or allergic diseases.
Do vaccines cause autoimmune diseases like diabetes and multiple sclerosis (MS)?
There is no evidence that vaccines cause autoimmune diseases such as diabetes and multiple sclerosis.
- Several studies have shown that vaccines are not associated with an increased risk of developing diabetes.
- Several studies have been done that have found no evidence that vaccines cause MS or flare-ups of MS.
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