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COVID-19: Get the latest updates or take a self-assessment.

What you need to know about COVID-19 vaccines: Information for people with cancer

This information is accurate as of September 13, 2022. Information about the COVID-19 vaccines is changing quickly. Ontario Health will update this handout as information changes.

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Read this information to learn about:

  • Why people with cancer should get vaccinated
  • How the vaccines work and how they are given
  • How many vaccine doses you may need
  • Possible side effects from the vaccines
  • Why it is important to follow public health rules after getting the vaccine

This information is meant to give you, your family and caregivers general information about the COVID-19 vaccines and what is known now.  

Check the websites of Ontario’s Ministry of Health and your local public health agency to find out more details. Call the Ontario Vaccine Information Line (1-888-999-6488) if you would like to use the phone.

Why should people with cancer get vaccinated?

People with cancer may have a higher risk of:

  • Getting COVID-19
  • Getting very sick from COVID-19
  • Dying from COVID-19

People with cancer should get all doses of COVID-19 vaccine that they are eligible for as soon as they can.

If you are at high risk of getting very sick from COVID-19, you must also be extra careful to protect yourself from getting infected. Limit your close contacts to people who are fully vaccinated.

Stay away from crowds and indoor places where you are not sure if others have been vaccinated.

How are the vaccines given?

The COVID-19 vaccines are a series of shots (needles) into your upper arm, like the flu shot.

How many COVID-19 vaccine doses will I need?

For most people, the COVID-19 vaccine is 2 doses, followed by booster shots. To get enough protection from the vaccine, some people with weakened immune systems (including many people with cancer) get 3 doses of COVID-19 vaccine, followed by booster shots.

Any dose of vaccine after your first 2 or 3 is called a booster shot. Booster shots are given when your vaccine protection starts to fade. They are usually given at least 3 months after your last dose. As time goes on, you will likely need more booster shots.

Keeping up to date on your booster shots is very important for everyone. Check with your local public health unit for recommendations about booster shots.

When is the best time to get the COVID-19 vaccine when being treated for cancer?

If you have not yet had any doses of vaccine, it is very important to get your first dose as soon as possible. Talk to your healthcare team if you have questions or concerns

If you are getting any of the treatments below, speak to your cancer care team about the best timing for your COVID-19 vaccine:

  • Chemotherapy
  • Immunotherapy
  • Stem cell transplant
  • Adoptive cell therapy
  • Immunosuppressive therapy (treatments that weaken your immune system)

How do the COVID-19 vaccines work?

The COVID-19 vaccines teach your body to make proteins that fight the COVID-19 virus.

You cannot get COVID-19 from any of the vaccines.

Which vaccine will I get?

The vaccine you get will depend on which vaccine is available in your area at the time of your appointment, your age, sex and other factors. There are several brands of vaccines being used in Ontario. They have all been tested, are shown to be safe and work well.

How do I know that the vaccines are safe?

Billions of doses of COVID-19 vaccines have been given to people all over the world. Serious side-effects from the vaccines are extremely rare.

The COVID-19 vaccines are safe for people with cancer. People with cancer should get fully vaccinated as soon as possible to avoid getting very sick from COVID-19.

What are possible side effects from the vaccines?

You may have mild side effects in the days after getting their vaccine. Most side effects will go away on their own.

The most common side effects from the vaccines are:

  • Pain, a change in colour, redness or swelling in your arm where the needle was given
  • Fatigue (tiredness)
  • Headache
  • Body aches and chills
  • Joint pain
  • Mild fever
  • Diarrhea
  • Vomiting
  • Swollen glands can happen for a few days after getting a COVID-19 vaccine. Talk to your cancer care team if this lasts for more than a few days.

If side effects last for more than 2-3 days, make sure you speak to your health care team.

Rare but serious side effects

In rare cases, COVID-19 vaccines have been linked to:

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

These serious side-effects have happened more in younger patients. For most people, the heart inflammation has been mild and has gone away quickly.

Some vaccine brands have had fewer reports of myocarditis than others. Check with your health care team to find out which brand is right for you.

Signs of myocarditis and pericarditis are:

  • chest pain,
  • shortness of breath or
  • heart palpitations (a fluttering or pounding heart)

Get medical help right away if you have any of these side effects after getting a COVID-19 vaccine.

Can the vaccine cause allergic reactions?

It is possible to be allergic to ingredients in the COVID-19 vaccines. Talk to your cancer care or your family health team before getting vaccinated if:

  • You have any serious allergies
  • You have had a serious allergic reaction to any other vaccines, drugs, or food

If you had an allergic reaction to your first dose of a COVID-19 vaccine:

  • You may need to see an allergist/immunologist or other health care provider before getting your second shot
  • You may need to get your vaccine in a hospital instead of at a clinic or pharmacy

For more information about ingredients in the vaccines, search the vaccine names on the Health Canada website or ask your health care team.

Do I need to keep following local public health rules after getting the vaccine?

Yes. Every local public health unit sets their own rules about protections for COVID-19. Check with your local public health unit to find out what is allowed in your area right now.

People with cancer who have a weakened immune system should consider:

  • Wearing a mask when in close contact with others, especially when indoors
  • Wash your hands often
  • Stay apart from other people unless you know that they are fully vaccinated

Are there times when I should wait to get the vaccine?

There are times when some people should wait to get the COVID-19 vaccine:

  • If you currently have COVID-19 you should wait to get the vaccine until after you recover from the virus. Even if you have already had COVID-19 you need to get your vaccine because it is possible to get the virus again. Talk to your health care team about when to get the vaccine after you recover.
  • If you have symptoms of COVID-19 or are currently self-isolating you should wait to get the vaccine. Talk to your health care team about your symptoms and getting a COVID-19 test. Your health care team will tell you when to get the vaccine.

It is safe to get your flu shot at the same time as your COVID-19 .

Speak to your surgical team about the best time to get your vaccine if you are having surgery.

For more information

Talk to your health care team for more information about the COVID-19 vaccines.

Health Canada

Ontario Ministry of Health

Public Health Unit locator


Provincial Vaccine Information Line

Call if you have questions about Ontario's COVID-19 vaccination program or booking your vaccination appointment. Information is available in multiple languages.

Telephone: 1-888-999-6488

TTY: 1-866-797-0007