COVID-19: Vaccine safety and side effects

On this page

Vaccine safety

Only vaccines that meet the safety, effectiveness and quality standards of Health Canada are approved for use in Canada. COVID-19 vaccines are tested during their development according to international standards and then carefully reviewed by Health Canada. The benefits of all COVID-19 vaccines continue to outweigh the risks of the disease.

The vaccines can't give you COVID-19 because they don't contain the virus that causes it.

Learn more about vaccine safety in Canada

mRNA vaccines

This type of vaccine helps your cells make a coronavirus protein. This protein will trigger an immune response that will help protect you against COVID-19. Once triggered, your body makes antibodies. These antibodies help you fight the infection if the real virus does enter your body in the future.

mRNA vaccines don't use a live virus to trigger an immune response. You can't get COVID-19 from the vaccine and it doesn't interact with your DNA or change it in any way.

Learn more about mRNA vaccines

Viral vector vaccines

This type of vaccine uses a harmless virus (in this case, an adenovirus) as a delivery system. This delivery system helps your cells to make a coronavirus protein.

The protein will trigger an immune response that will help protect you against COVID-19. The adenovirus isn't the virus that causes COVID-19. You can't get COVID-19 from the vaccine.

Learn more about viral vector vaccines

Protein subunit vaccines

Protein subunit vaccines contain harmless and purified pieces (proteins) of the virus, which have been specifically selected for their ability to trigger immunity. Once vaccinated, your immune system triggers an immune response that will help protect you against COVID-19.

Protein subunit vaccines are already used to protect against other diseases, such as hepatitis B. They can't cause COVID-19 because they only contain small purified pieces of proteins and not the virus itself.

Learn more about protein subunit vaccines

Plant-based vaccines

This type of vaccine uses plant-based technology. The virus' genetic code is delivered to the leaf cells of the plant using harmless bacteria. The plant's natural cell process is used to produce a non-infectious virus-like particle that mimics the spike virus that causes COVID-19. Your body's immune system then responds to it in the same way it would if it encountered the real virus.

Through this process, your body can mount a strong immune response without exposing you to the virus that causes COVID-19.

Learn more about plant-based vaccines

Common side effects

After being vaccinated, it's common and normal to have temporary side effects, even after a COVID-19 infection. These usually last from a few hours to a few days after vaccination. This is the body's natural response, as it's working hard to build immunity against the disease.

People react differently after being vaccinated. Even if you experience temporary side effects, keep up to date on the vaccinations recommended for you, including booster doses. This will help protect you from serious outcomes from COVID-19.

Common vaccine side effects may include:
Symptoms at the injection site, such as: More general symptoms, such as:
  • redness
  • soreness
  • swelling
  • chills
  • fatigue
  • joint pain
  • headache
  • mild fever
  • muscle aches

Evidence indicates that vaccines and boosters are effective at helping to prevent serious illness, hospitalization and death due to COVID-19. Evidence indicates that the benefits of COVID-19 vaccines continue to outweigh the risks of the disease. Receiving an mRNA booster dose provides even better protection.

Managing common side effects at home

You can take over-the-counter medicine after your vaccination to help with any pain or to lower a fever.

For pain where the needle was given, you can:

  • apply a clean, cool, wet washcloth over the area that received the injection
  • gently use or stretch your arm

Contact a health care provider if:

  • you have questions about how to manage any symptoms
  • you're concerned about any symptoms you're experiencing after vaccination

Learn more about:

COVID-19 vaccine ingredients

The active components in many vaccines are called antigens. Antigens are the parts of germs that teach the body's immune system to recognize and attack the real germ. mRNA and viral vector vaccines contain the instructions for the body to make a coronavirus protein. That coronavirus protein is the antigen.

Vaccines also contain small amounts of other ingredients, which each serve specific purposes. These ingredients aren't harmful and leave the body a few days after vaccination. In some cases, some people might be sensitive to specific ingredients, which can result in an allergic reaction.

Learn more about:

Ingredients by vaccine

COVID-19 vaccines approved in Canada don't contain common food allergens, such as eggs, shellfish, gluten or nuts. They also don't contain antibiotics or latex.

Each vaccine developed for COVID-19 may have different ingredients. Learn more about the ingredients for the:

Allergic reactions

Allergic reactions are rare, but they do happen. Although they can be serious, allergic reactions are treatable.

Speak with an allergist or your health care provider about any serious allergies or health conditions you may have before you get a vaccine.

Symptoms of an allergic reaction usually come on shortly after and up to a few hours after vaccination and include:

If you develop or witness any serious symptoms that could be an allergic reaction (anaphylaxis) after vaccination:

Contact your health care provider if you experience:

Learn more about:

mRNA allergic reactions and future doses

It's possible for most people who experienced an allergic reaction to a COVID-19 vaccine to safely receive future doses of that same vaccine. This includes with an mRNA vaccine.

The National Advisory Committee on Immunization has recommendations for people who experienced a severe immediate allergic reaction after a first dose of an mRNA COVID-19 vaccine. People with a history of a severe immediate allergic reaction after a first dose of an mRNA COVID-19 vaccine should:

  • consult with an allergist or another appropriate health care provider before receiving future doses of an mRNA COVID-19 vaccine
  • receive future doses of an mRNA COVID-19 vaccine in a controlled setting with someone who is experienced in managing anaphylaxis
  • be observed for at least 30 minutes after vaccination
    • the normal observation period for people who haven't experienced a severe immediate allergic reaction after vaccination is 15 minutes

If you know you're allergic to a component of an mRNA COVID-19 vaccine, consult with an allergist or your health care provider. It may still be possible for you to receive these vaccines.

Rare reactions that have been reported

As with all vaccines, there's a very small chance that there will be a serious side effect. Reports of side effects in Canada, including the rare reactions described below, continue to be monitored closely by:

Health Canada is:

Learn more about:

mRNA vaccines

Myocarditis and pericarditis

Rare reactions have been reported following vaccination with mRNA COVID-19 vaccines related to:

  • myocarditis (inflammation of the heart muscle)
  • pericarditis (inflammation of the lining around the outside of the heart)

Seek immediate medical attention if you experience any of the following symptoms after getting a vaccine:

  • chest pain or pressure
  • irregular heartbeat or rhythm, including too quick, too slow or an irregular pattern of heartbeat
  • shortness of breath

Myocarditis and pericarditis seem to be occurring more often than expected in some populations and situations, such as:

  • in adolescents and young adults
  • in males
  • following the second dose
  • typically occurring within 7 days after vaccination

In the majority of cases, symptoms of myocarditis or pericarditis resolve quickly after seeking medical care.

Additional doses and booster doses

In most cases, someone who has had myocarditis or pericarditis after an mRNA vaccine should defer receiving another dose.

The rates of these conditions after the booster dose with an mRNA vaccine appear to be somewhat lower than after the second dose. Some people with confirmed myocarditis or pericarditis may choose to receive another dose after discussing the risks and benefits with their health care provider.

Bell's palsy (facial paralysis)

We've seen a small number of reports of people developing this rare disorder after receiving a COVID-19 mRNA vaccine.

Bell's palsy is an episode of facial muscle weakness or paralysis. Symptoms appear suddenly and generally start to improve after a few weeks. This condition generally affects nerves on one side of the face.

In the majority of cases, it's temporary. However, in very rare cases, Bell's palsy can be permanent.

Contact your health care provider if you have any of these symptoms:

  • mild weakness to total paralysis on one side of the face, affecting facial muscle movement, such as:
    • smiling
    • squinting
    • blinking or closing the eyelid, which may result in tearing from the eye
  • headache
  • loss of feeling in the face
  • hypersensitivity to sound in the affected ear
  • loss of the sense of taste on the front two-thirds of the tongue

The symptoms of Bell's palsy may look like other conditions or medical problems. Always see your health care provider for a diagnosis.

Viral vector vaccines

Blood clots with low platelets

Blood clots with low levels of blood platelets that occur after vaccination with viral vector vaccines (AstraZeneca Vaxzevria/COVISHIELD and Janssen Jcovden) are rare but serious.

These serious side effects have been reported to begin up to about a month after vaccination. Quick diagnosis and treatment is critical to reduce the risk of negative outcomes.

Seek immediate medical attention if you experience any of the following symptoms:

  • shortness of breath
  • chest pain
  • persistent abdominal pain
  • blurred vision
  • confusion or seizures
  • severe, persistent or worsening headache
  • skin bruising or tiny blood spots under the skin (sometimes away from the part of your body the needle went in)
About the condition

Scientists and doctors are still working to understand this condition involving blood clots (thrombosis) with low platelets (thrombocytopenia). The condition is being referred to as thrombosis with thrombocytopenia syndrome (TTS).

If blood tests are positive for antibodies that affect platelets, this condition is also being called vaccine-induced immune thrombotic thrombocytopenia (VITT).

Thrombosis with thrombocytopenia syndrome is different from more common blood clotting issues, such as deep vein thrombosis or pulmonary embolism.

With thrombosis with thrombocytopenia syndrome, blood clots can form in different parts of the body, including the brain (called cerebral venous sinus thrombosis) and in the abdomen.


This is a blood clot, which prevents blood from flowing normally.


This is a condition in which you have a low blood platelet count.

Platelets (thrombocytes) are blood cells that help blood clot. Platelets stop bleeding by clumping and forming plugs in injured blood vessels. Low platelets may lead to the bruising, which can be seen with thrombosis with thrombocytopenia syndrome.

Learn more about:

Capillary leak syndrome

A very small number of reports of this rare condition have been reported following vaccination with the AstraZeneca Vaxzevria/COVISHIELD and the Janssen Jcovden vaccine. Some of the reports reviewed were in individuals who have had this condition previously.

Capillary leak syndrome is very rare, but can be serious. The condition causes fluid leakage from small blood vessels (capillaries). This can result in:

  • low blood pressure
  • swelling, mainly in the arms and legs
  • sudden weight gain

If you have any of the above symptoms in the days after vaccination, you should seek medical attention immediately. You shouldn't get the AstraZeneca Vaxzevria/COVISHIELD or the Janssen Jcovden viral vector vaccine if you've previously experienced capillary leak syndrome.

Guillain-Barré syndrome (GBS)

There are a small number of reports of people who have developed this rare disorder after receiving the COVID-19 viral vector vaccine.

Guillain-Barré syndrome is a rare neurological disorder that causes the body's immune system to damage nerve cells. This can result in:

  • pain
  • numbness
  • muscle weakness, progressing to paralysis in the most severe cases

Most people fully recover from the disorder. Seek medical attention right away if you have any of these symptoms after getting vaccinated. Symptoms can start between 3 and 25 days after vaccination.

Ongoing monitoring of side effects and reactions

As the COVID-19 vaccine rollout continues across Canada, safety monitoring is ongoing. The Public Health Agency of Canada, Health Canada, and provincial and territorial health authorities continue to:

As safety issues are investigated, Health Canada will take appropriate action as needed. Reports and investigations of safety concerns show that Canada's vaccine safety monitoring system works.

We encourage anyone who witnesses or experiences a possible reaction to a vaccine to report it to their health care provider.

Health care providers should report possible reactions following vaccination to their local public health authority. The public health authority then reports them to the Public Health Agency of Canada through their provincial or territorial public health authorities.

Learn more about:

Vaccine manufacturers

Vaccine manufacturers also have a responsibility to monitor and take action on safety issues, including reporting them to Health Canada. They're required to develop and update a detailed product monograph and a risk management plan.

The product monograph provides the necessary information for the safe and effective use of a drug or vaccine. This ensures health care providers and the public are aware of all safety information.

A risk management plan:

In addition, Health Canada regularly updates a post-authorization activity table for all COVID-19 vaccines and treatments. This table summarizes all activities that have happened following approval, including product monograph changes for:

Related links

Page details

Date modified: