COVID-19 mRNA Vaccines: What you need to know

Health Canada approved COVID-19 mRNA vaccines that are safe, effective, and can help save millions of lives. But you may be wondering what exactly are mRNA vaccines? Here we break down everything you need to know about the COVID-19 mRNA vaccines.

What Is mRNA?

Messenger ribonucleic acid (mRNA) is a type of genetic information found in our cells. mRNA can be thought of as a set of instructions that are used by your cells to make different proteins in your body.

How Do COVID-19 mRNA Vaccines Work?

COVID-19 mRNA vaccines work by giving genetic instructions (mRNA) to create a harmless protein of the virus called a spike protein, teaching your body to recognize and fight the virus. 1,2,3 The spike protein is found on the surface of the virus.

After getting the vaccine, your body will read the genetic instructions (mRNA) like a recipe and make the spike protein. Once the spike protein has been made, the cell will break down the mRNA and get rid of them. The mRNA never enters the cell’s nucleus, where your DNA is stored, so it will not affect your DNA in any way. 1,2,3

Next, the spike protein is displayed on the surface of the cell. Your immune system recognizes the spike protein since it doesn’t typically belong there. This triggers an immune response in your body to make antibodies, which will protect you from getting sick if the real virus enters your body in the future. 1,2,3

mRNA Vaccine Technology Is Not Brand New

While the COVID-19 vaccines are the first mRNA vaccines to ever be approved, mRNA vaccine research has actually been going on for decades. There have been early clinical trials in the past using mRNA vaccines for other diseases such as the flu, Zika virus, rabies and cytomegalovirus (CMV).1 Since then, there have been many advancements and a lot of fine-tuning in mRNA vaccine technology, which has made the development of the COVID-19 mRNA vaccines possible today. mRNA vaccines can be developed faster than other traditional vaccines, since they are created in a laboratory using materials that are readily available.1

Are mRNA Vaccines Safe?

People may be concerned about live vaccines, which use a weakened version of the virus. For some people, such as those with weakened immune systems, these types of vaccines can possibly cause the disease they are meant to protect against.4 Unlike live vaccines, mRNA vaccines do not contain the live virus, so there is no risk of developing COVID-19 if you get vaccinated with one of the mRNA vaccines.

The COVID-19 mRNA vaccines were reviewed to ensure that they meet the same rigorous safety standards as any other vaccine that has been approved by Health Canada.1 That includes studying and monitoring the safety of the vaccines in large clinical trials, as well as after approval, once the vaccines are on the market. 

The side effects commonly seen with the COVID-19 mRNA vaccines are similar to those seen with other vaccines. They are mild to moderate, and usually resolve on their own in a few days. They include: 2,3

  • injection site pain
  • fatigue
  • headache
  • muscle pain
  • chills
  • joint pain
  • fever

As with all vaccines, there is a rare chance of having a serious allergic reaction, which can include hives (itchy bumps on the skin); swelling of the face, tongue or throat; and difficulty breathing.

Individuals who have a severe allergic reaction to polyethylene glycol (PEG), an ingredient found in certain medications and medical products, should not receive an mRNA vaccine.5 Those who experience inflammation of the heart muscles (myocarditis) or the tissue lining the heart (pericarditis) after their first dose of an mRNA vaccine should not get their second dose of an mRNA vaccine.5

Health Canada will continue to review the safety data of the mRNA vaccines and may take additional safety measures, if needed, to protect the health and safety of Canadians.

If you have any further questions or concerns about mRNA vaccines, you can speak to your pharmacist at your local Shoppers Drug Mart store.

If you are interested in reading more about the COVID-19 vaccines, click here.


  1. Government of Canada. COVID-19 mRNA vaccines., Last updated September 16, 2021. Accessed October 12, 2021.
  2. Government of Canada. Pfizer-BioNTech COVID-19 vaccine: What you should know., Last updated September 24, 2021. Accessed October 12, 2021.
  3. Government of Canada. Moderna COVID-19 vaccine: What you should know., Last updated October 8, 2021. Accessed October 12, 2021.
  4. Frequently asked questions about vaccine safety. Immunize BC. (2020). Last updated March 24, 2020. Accessed October 12, 2021.
  5. Government of Canada. Recommendations on the use of COVID-19 vaccines. Last updated September 28, 2021. Accessed October 12, 2021.