COVID-19 vaccines and cancer

The most common side effects from the mRNA vaccines are:

• Fatigue (tiredness)
• Headache
• Muscle aches
• Pain where you got the shot (on your upper arm)
• Redness and swelling where you go the shot (on your upper arm)
• Joint pain
• Mild fever
• Swollen glands (this happens less often)

If you get a vaccine that has two doses, these side effects are more likely to happen after the second dose. Speak to your health care team if these side effects last for more than three days.

Serious side effects from the vaccine are rare. If you get any of these side effects within three days of getting the vaccine, call your health care team right away or go to your nearest emergency department. These serious side effects include:

• Hives (bumps on the skin that are often very itchy)
• Swelling of the face or mouth
• Trouble breathing
• Very pale colour in your face or serious drowsiness (feeling very sleepy)
• Very high fever (over 40°C)
• Convulsions (spasm or shaking) or seizures (fit of uncontrolled movements)
• Numbness or feeling of 'pins and needles'

If you have serious allergies or have had a serious allergic reaction to other vaccines, drugs or food, talk to your cancer doctor before you get the COVID-19 vaccine.

Talk to your cancer doctor before you get a COVID-19 vaccine if you have serious allergies or had an anaphylaxis reaction (very serious allergic reaction that could cause you to stop breathing) to:

• Other vaccines
• Other medicines, including cancer medicines like chemotherapy
• Any foods

If you have had a serious allergic reaction to any of the ingredients in any of the vaccines, talk to your doctor about your options. If you are allergic to an ingredient in one company’s vaccine you may be able to get a different vaccine.

For a complete list of ingredients in the four approved vaccines, visit covid-19.ontario.ca/covid-19-vaccines-ontario. 

The best vaccine is the first one you can get.

• You may have heard or read about the efficacy rates for each vaccine. A vaccine’s efficacy rate refers to how well the vaccine did in clinical trials under ideal conditions.
• The conditions for each COVID-19 vaccine clinical trial were different and cannot be compared to each other. The clinical trials were set up differently, measured different things and run during different times of the pandemic.
• For example, each clinical trial had a different definition for what counted as COVID-19 infection.
  • Some clinical trials counted one mild symptom as a COVID-19 infection while others counted two mild symptoms or one moderate symptom.
  • Some clinical trials counted COVID-19 symptoms one week after the second dose while others counted symptoms two weeks after the second dose.

All the COVID-19 vaccines protect you equally against getting very sick if you get COVID-19.

At this time, we do not know how long the vaccine will last. Since these are new vaccines, they will need to be studied over time to see how long protection lasts.

COVID-19 vaccines are given in the upper arm muscle just like a flu shot.

• The Pfizer, Moderna and AstraZeneca vaccines are given in two doses.
• The Johnson & Johnson vaccine is given in one dose.

It takes time for your body to build up an immune response to protect you.

• If you get a vaccine that needs two doses (like Pfizer, Moderna, or AstraZeneca), you will have some protection after the first dose. You need a second dose for full protection.
• If you get the Johnson & Johnson vaccine, it takes at least two weeks for the vaccine to protect you from getting very sick from COVID-19.

Yes. You still need to wear masks and practice physical distancing until a large number of people get the vaccine. It is also unknown at this time whether the vaccine provides long-term protection from COVID-19.