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Frequently asked questions about the COVID-19 vaccine

Vaccine & cancer

View our Q&A for Odette Cancer Centre patients »

Third dose information for Odette Cancer Centre patients »

Vaccine & heart disease

View our Q&A for Schulich Heart Program patients »

Vaccine development

How is it possible for a vaccine to go from the early stages of development to mass production and distribution in less than a year? Shouldn’t the manufacturers take more time to make sure this vaccine is safe?

Normally, vaccines and medications have longer development periods that take a couple of years to move from the lab to clinical use. However, given the focused energy and global need for a vaccine, many of the hurdles encountered in normal product development have been overcome in a record amount of time. To accomplish this, the researchers used strategies like combining phases of a clinical trial (eg. designing a Phase I/II trial) in order to get more data sooner that can help save time.

Importantly, lots of resources (financial, scientific, logistical etc.) were put into vaccine programs allowing the research to progress rapidly. Despite the tightened timeframe, approving bodies across the world in the United Kingdom, United States and Canada have conducted thorough reviews of the process and have deemed the vaccine to be safe.

How was the vaccine actually developed?

The COVID-19 pandemic has helped accelerate the development of new and innovative vaccine technologies – including messenger RNA (mRNA).

The mRNA vaccines contain the genetic code for producing “spike” proteins – the distinctive protrusions that dot the surface of the coronavirus. When delivered in a vaccine, the mRNA enters the body’s cells and instructs them to churn out spike proteins. Human cells immediately recognize these are “foreign” proteins and alert the immune system to start generating protective antibodies.

The key advantage of an mRNA vaccine is that the synthetic raw materials can be produced faster than some traditional vaccines, like flu shots, which rely on viral samples grown in eggs.

Safety/side effects

What is the difference between the four Health Canada-approved COVID-19 vaccines?

We’re very pleased there are four approved vaccines for COVID-19 in Canada and they are all highly effective and safe. Some patients have asked if one vaccine is better than the other. Our response is that the best vaccine is the vaccine that is available to you now regardless of age or underlying conditions. All available COVID-19 vaccines offer significant protections and save lives – so any vaccine is better than no vaccine, especially as variants emerge.

I’ve heard reports in the news of people experiencing side effects after getting the vaccine. What are they?

Some common expected side effects include:

  • Pain or swelling where the vaccine was given
  • Tiredness
  • Headache, fever
  • Chills
  • Muscle or joint soreness
  • Nausea and vomiting

Although some of the side effects of the vaccine are similar to symptoms of COVID-19 infection, the symptoms are normal signs that your immune system is doing its job, and not due to the COVID-19 infection. You CANNOT get COVID-19 from the vaccine. Symptoms such as cough or other respiratory symptoms are not known side effects of the vaccine and are more likely to be due to a respiratory infection.

Some people are fortunate and do not experience any symptoms after getting the vaccine. If you do not experience any of the symptoms, this in no way indicates whether the vaccine has “worked” or not.

How do we know the COVID-19 vaccine manufacturers properly evaluated the safety of the vaccine during clinical trials?

Throughout the vaccine trials, progress was (and continues to be) closely tracked by an external group of independent experts, called a Data Monitoring Committee (DMC), which also monitors studies for safety on an ongoing basis. To date, the Data Monitoring Committee for the study has not reported any serious safety concerns related to the vaccines. More information is available on each manufacturer's website. Importantly, all the safety data was reviewed independently by organization such as Health Canada as requirement for vaccine approval.

How can we trust that the vaccine will be safe long-term?

There is a rigorous testing process that happens before a vaccine gets approved, and safety is a key factor that is examined. Follow-up studies are also conducted on vaccines to look at longer-term effects. The vaccines currently approved for other diseases (e.g. flu, hepatitis B etc.) all have excellent safety profiles, and the same standards apply to any COVID-19 vaccine used in Canada.

Is it possible that getting the COVID-19 vaccine could actually give me the virus?

No. The vaccine only contains parts of the virus, such as a protein from the virus, or a bit of the genome. This is what allows your immune system to be trained to recognize SARS-CoV-2 later if you get infected, and keeps you protected from it.

How many doses do people need to get for the vaccine to work?

Some COVID-19 vaccines, such as those produced by AstraZeneca, Moderna and Pfizer-BioNTech, require two doses. Others, such as the Johnson & Johnson vaccine, only require one dose. Recently, the National Advisory Committee on Immunization (NACI) recommends some people with certain illnesses or on certain treatments get three doses of COVID-19 vaccine.

Is it ok if my second dose is manufactured by a different brand than my first dose?

The National Advisory Committee on Immunization (NACI) guidelines state that if you had Moderna or Pfizer for your first dose, you can safely take either Moderna or Pfizer for your second dose. NACI has made this recommendation because these two vaccine brands use mRNA technology, meaning they are interchangeable.

» Read a Q&A with a Sunnybrook microbiologist about mixing mRNA COVID-19 vaccines

Can people who are pregnant, breastfeeding or trying to conceive get the COVID-19 vaccine?

More vaccine resources

Get information about COVID-19 vaccination in Toronto

Do you have more questions about COVID-19 vaccines?

The Provincial Vaccine Confidence Line can be accessed by calling 1-833-943-3900 or 1-866-797-0007 (TTY for people who are deaf, hearing-impaired or speech-impaired). The service is available in more than 300 languages, seven days a week from 8:00 a.m. to 8:00 p.m.