COVID-19: Vaccine safety and side effects

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Vaccine safety

Only vaccines that meet Health Canada's regulatory requirements for safety, effectiveness and quality are approved for use in Canada. COVID-19 vaccines reduce the risk of severe illness, death and post COVID-19 condition (long COVID).

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Common side effects

The COVID-19 vaccines work with the body's natural defences to develop protection against COVID-19. The body does this without the risks that come from being infected.

After being vaccinated, it's common to have some minor side effects. This is normal and reflects the body's natural response to vaccination, as it's working to build immunity against the disease. These side effects usually last from a few hours to a few days after vaccination.

Common vaccine side effects may include symptoms at the injection site, such as:

More general symptoms include:

Managing common side effects at home

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

For pain where the needle was given, you can:

Contact a health care provider if:

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Allergic reactions

Vaccines contain a number of ingredients and some may cause allergic reactions in some individuals on rare occasions. Allergic reactions to the COVID-19 vaccines are rare, but they have been reported. Although some allergic reactions can be serious, they can be managed.

You may be asked to stay at the clinic for a period of time after vaccination to make sure you don't develop an allergic reaction.

Many people who have experienced an allergic reaction to a COVID-19 vaccine have safely received additional doses of that same vaccine after consultation with an allergist or other appropriate health care provider.

Speak with your health care provider or local public health unit if you have questions about allergic reactions before you get a COVID-19 vaccine.

Symptoms of an allergic reaction

Symptoms of an allergic reaction usually come on shortly after vaccination but may appear hours later. They may include reactions like difficulty breathing, hives and swelling of the face or airway.

If you have symptoms that could be an allergic reaction, seek immediate medical attention.

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Rare reactions

Serious reactions following vaccination are rare. After a COVID-19 vaccine, there's a very small chance that there will be a serious side effect. The following conditions are rare side effects that have been reported in Canada after COVID-19 vaccination.

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Bell's palsy (facial paralysis)

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.

There have been a small number of reports of people developing this rare disorder after receiving the mRNA COVID-19 vaccines.

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:

  • weakness or paralysis on one side of the face, affecting facial muscle movement, such as:
    • smiling
    • squinting
    • blinking or closing the eyelid, including excess tearing from the eye
  • unusual headache, not relieved by over the counter remedies
  • loss of feeling in the face
  • hypersensitivity to sound in one ear
  • loss of the sense of taste on part or all 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.

Blood clots with low platelets

Thrombosis is a blood clot which prevents blood from flowing normally.

Thrombocytopenia is a condition in which you have a low blood platelet count. Platelets (thrombocytes) are blood cells that help blood to clot. Platelets stop bleeding by clumping and forming plugs in injured blood vessels.

Blood clots with low levels of blood platelets occurred after vaccination with the following viral vector COVID-19 vaccines:

  • AstraZeneca Vaxzevria/Covishield
  • Janssen Jcovden (Johnson and Johnson)

These serious side effects were very rare but serious, and have been reported to begin up to about a month after vaccination. These vaccines are either no longer recommended or approved in Canada.

About the condition

This condition involving blood clots (thrombosis) with low platelets (thrombocytopenia) is referred to as thrombosis with thrombocytopenia syndrome (TTS).

In Canada, if blood tests are positive for antibodies that affect platelets, this condition has been called vaccine-induced immune thrombotic thrombocytopenia (VITT).

TTS is different from more common blood clotting issues, such as deep vein thrombosis or pulmonary embolism.

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

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)

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Capillary leak syndrome

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

A very small number of reports of this rare condition have been reported after vaccination with the following viral vector COVID-19 vaccines:

  • AstraZeneca Vaxzevria/Covishield
  • Janssen Jcovden (Johnson and Johnson)

Capillary leak syndrome is very rare, but can be serious. Some of the reports reviewed were in individuals who have had this condition previously. These vaccines are either no longer recommended or approved in Canada.

If you have any symptoms in the days after vaccination, seek medical attention immediately. You shouldn't get the AstraZeneca Vaxzevria/Covishield vaccine if you've previously experienced capillary leak syndrome.

Guillain-Barré syndrome (GBS)

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

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

  • AstraZeneca Vaxzevria/Covishield
  • Janssen Jcovden (Johnson and Johnson)

These vaccines are either no longer recommended or approved in Canada.

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

Myocarditis and pericarditis

Myocarditis is inflammation of the heart muscle. Pericarditis is inflammation of the lining around the outside of the heart.

These rare reactions have been reported following vaccination with the:

  • mRNA COVID-19 vaccines
  • protein-based Novavax Nuvaxovid vaccine
  • viral vector Janssen Jcovden (Johnson and Johnson) vaccine

Myocarditis and pericarditis seem to occur more often 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.

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 or too slow
  • shortness of breath

Ongoing safety monitoring

Canada has reliable systems in place to monitor the safety of COVID-19 vaccines.

Vaccine safety monitoring involves a collaboration of many different groups, including:

Anyone who experiences a possible reaction to a vaccine and is concerned should report it to their health care provider.

Health care providers should report possible reactions to their local public health unit. Public health units will report the event to their provincial or territorial public health authority and on to the Public Health Agency of Canada. Health care providers can use the following information to help make a report:

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Vaccine manufacturers

Vaccine manufacturers also have a responsibility to monitor and take action on safety issues, as they work with their international partners.

Their responsibility includes reporting serious reactions and safety issues to Health Canada. They're required to:

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