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

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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
  • Possible side effects from the vaccine
  • 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-191
  • Getting very sick from COVID-192
  • Dying from COVID-191,2,3,4,5,6,7

People with cancer should get both doses of the COVID-19 vaccine as soon as they can.

The sooner that most people in Ontario get fully vaccinated, the sooner life can go back to normal.

What groups of people with cancer are most at risk?

The following groups of people with cancer have an even higher risk of getting very sick from COVID-19. Those who:

  • Are 65 years or older8
  • Have had a stem cell transplant in the last 6 months9
  • Are getting or have recently stopped having cancer treatments10
  • Have been diagnosed with cancer in the last year1
  • Have cancers of the blood like leukemia, lymphoma and multiple myeloma3,11,12,13
  • Have lung cancer3,12,13,14
  • Have cancer that has spread to another area of the body (metastatic cancer)2
  • Have had cancer surgery within the last 2 months2,14

If you are in one of the above groups, you must be extra careful to protect yourself from getting COVID-19.

Stay away from crowds and indoor settings where you are not sure if others have been vaccinated, such as concerts, places of worship, and gyms.

How do the COVID-19 vaccines work?15

There are 3 vaccines that are being used in Ontario.

The COVID-19 vaccines from Pfizer and Moderna are messenger RNA (mRNA) vaccines. mRNA is a type of molecule (small part of a cell) that our bodies are always making. mRNA vaccines teach our bodies to make proteins that tell our immune systems to fight the COVID-19 virus.

The COVID-19 vaccine from AstraZeneca may also be called Covishield. It is a viral vector vaccine. This type of vaccine uses a harmless virus (not COVID-19) to teach your body to build up immunity to COVID-19 without making you sick. The flu shot is also a viral vector-based vaccine.

You cannot get COVID-19 from either type of vaccine.

When is the best time to get a vaccine?

You should get both of your vaccine doses as soon as you can.

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

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

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 and other factors. Your second dose may not be the same as your first dose. Mixing vaccine types has been shown to be safe and to work well.

How are the vaccines given?

The COVID-19 vaccine doses are given as shots (needles) into your upper arm, like a flu shot. The Pfizer, Moderna and AstraZeneca (Covishield) vaccines are 2 doses.

Your second dose will be given weeks after the first dose. When booking your vaccine appointment, ask about the timing of your second dose to make sure it follows the advice of your cancer care team.

How do I know that the vaccines are safe?

All vaccines in Canada meet very strict safety and efficacy (how well something works) standards before they are approved for use.16 Health Canada has one of the most careful review processes in the world.

The vaccines:

  • Were tested on thousands of people and have been given to millions of people across the world
  • Have met all the requirements for approval, including safety
  • Will continue to be watched for any issues as they are used across the world

The COVID-19 vaccines are safe for people with cancer.16,17,18 People with cancer should get fully vaccinated as soon as possible to avoid getting very sick from COVID-19.

How well do the vaccines work for people with cancer?

All the vaccines used in Ontario have been shown to work well in large clinical trials (research studies that involve humans). The vaccines work well to prevent COVID-19 infections, hospitalizations and death.

People with weakened immune systems, including some people with cancer, may not get as much protection from the vaccine doses as others. If you have a weakened immune system, you may not get as much protection from your first dose alone and you may not get the full protection even after 2 doses of the vaccine.19,20,21To get the most protection possible, you must get both vaccine doses as soon as possible.To keep you safe, the people close to you should also get fully vaccinated as soon as possible.

Studies have also shown that the vaccines work well against the variants that we know of right now.22

How soon does the vaccine start to work and how long does it last?23,24,25,26,27,28,29

You will begin to get protection from the vaccine about 2 weeks after your first shot. You will have the most protection possible about 2 weeks after the 2nd shot.

At this time, we do not know how long protection from the vaccine will last. Since the vaccines are new, they will need to be studied over time to see how long they will work. It is possible that people with cancer will need a booster vaccine in the future.30,31,32,33,34,35,36

What are possible side effects from the vaccines?

Some people may have mild side effects in the days after getting their vaccine. Side effects may be worse after your second dose. Most side effects will go away on their own.

The most common side effects from the vaccines are:16,24,26,27,28,37,38,39

  • Pain, discolouration, redness or swelling in your arm where the needle was given
  • Fatigue (tiredness)
  • Headache
  • Body chills
  • Muscle aches
  • 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.24,26,40,41,42

After you get the COVID-19 vaccine, wait for at least 15 minutes before going home. This wait is to check for side effects or an allergic reaction.

Rare but serious side effects

A rare but serious form of blood clots has been linked to the AstraZeneca vaccine.43 These clots are different than those that can be caused by cancer and cancer treatments. Most cases of the rare blood clots happen within 4 weeks (28 days) of the first dose of the AstraZeneca vaccine.28,44,45,46,36

The AstraZeneca vaccine has also been linked to very rare cases of capillary leak syndrome (CLS), a condition that causes fluid to leak from small blood vessels (capillaries) in your body. This can cause dizziness, fainting and swelling and in severe cases may cause trouble breathing. People who have had CLS before should not get the AstraZeneca vaccine.47

There have been rare reports of myocarditis (inflammation of the heart muscle) or pericarditis (inflammation of the lining of the heart) in people who have had mRNA vaccines. The heart inflammation has happened more in younger patients and, in most situations, it has been mild and people have gotten better quickly. Get medical help right away if you have chest pain, shortness of breath or heart palpitations (a fluttering or pounding heart) after getting an mRNA vaccine.48,49

Can the vaccine cause allergic reactions?

It is possible to be allergic to ingredients in the COVID-19 vaccines.50,51,52 If you have any serious allergies or have had a serious allergic reaction to other vaccines, drugs, or food, talk to your cancer care team or your family health team before you get the COVID-19 vaccine.

If you had an allergic reaction to your first COVID shot you may need to see an allergist/immunologist before getting your second shot. You may also 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 public health rules after getting the vaccine?

Yes. It may still be possible for fully vaccinated people to carry and spread COVID-19.53,54,55 Check with your local public health unit to find out what is allowed in your area right now.

After getting the vaccine it is important for people with cancer who have a weakened immune system to:

  • Keep 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 vaccinated56

You must keep following public health measures because:

  • It takes time for your body to build up protection after getting the vaccine
  • If you have a weakened immune system you may not get the full protection even after 2 doses of the vaccine
  • It is possible for COVID-19 to spread even between people who have already gotten the vaccine
  • We need to control the spread of COVID-19 in our communities until everyone has had both vaccine doses

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.
  • If you need to get another type of vaccine (such as the flu shot) wait at least 28 days after getting your second dose of the COVID-19 vaccine before getting any other vaccines.57,58

Speak to your surgical team about the best time to get your vaccine if you are having surgery.59

How did research teams develop the vaccines so quickly?

Researchers have been studying mRNA vaccines for many years. They were able to develop the COVID-19 vaccines quickly because:

  • The COVID-19 virus is similar to other viruses that researchers already knew a lot about
  • Research teams around the world started to work on the vaccine right away when the COVID-19 virus was found
  • Research teams all over the world shared information with each other
  • Many people quickly signed up for clinical trials (a research study that involves humans) to test the vaccines. For example, over 200,000 people in Britain took part in clinical trials.

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

Ontario Government Ethical Framework for COVID-19 Vaccine Distribution


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


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