COVID-19 Vaccines (Pfizer-BioNTech and Moderna) – How They Work



Having the first batches of vaccines to prevent COVID-19 available in Canada is great news! We now have a powerful way to protect our frontline health care professionals, Elders, loved ones, ourselves and our communities. 

It is understandable that many people will have questions as COVID-19 vaccination programs ramp up. To keep you informed so you can make the right decision for you and your family, the Medical Officers at the FNHA will be answering questions and providing new information as it becomes available. Today we are providing information on how the two new COVID-19 vaccines teach your body to protect itself against coronavirus, the virus that causes COVID-19. 

COVID-19 and mRNA vaccines

As soon as scientists identified COVID-19 as a deadly infectious disease, they began working to develop vaccines for the virus that causes it, SARS-CoV-2.

The Pfizer-BioNTech and the Moderna vaccines are now available in Canada. They have undergone rigorous clinical testing and Health Canada has approved them as safe for use. Both of these vaccines use messenger RNA (mRNA) to teach our cells how to make a protein that will trigger an immune response. Our body then makes antibodies that help us fight the infection if we contract the real virus.

The Pfizer-BioNTech and Moderna mRNA vaccines don’t include any parts of the SARS-CoV-2 virus. Instead, they contain instructions, like a recipe, that tells your cells to make a harmless piece of protein that makes up the coronavirus’ spikes.

The vaccine has no impact on your DNA (genetic material). After your cells make the spike protein, the cells destroy the mRNA. This mRNA never enters the central part (nucleus) of the cell where your DNA is found.

Your cells then display the spike proteins on their surface. Your immune system recognizes that the newly created spike protein is a foreign substance, and it begins making antibodies as part of its immune response.

If COVID-19 enters your body after you have been vaccinated, your immune system knows exactly what to do because it has “seen” the spike proteins before. Your immune system recognizes the coronavirus as a foreign susbstance and it will know how to destroy the virus before it can make you sick. Studies have shown that people who have had the vaccine are  at a far lower risk to contract COVID-19, and if they do, they are much less likely to have severe illness or die.

After you are vaccinated, you might feel some pain around where you received your injection and mild flu-like symptoms. These are signs that your vaccine and your immune system are working. For more info on vaccines and your immune system, keep reading or visit the Government of Canada webpage on the COVID-19 mRNA vaccines.

Looking ahead

It will be many months before enough people in BC have been vaccinated for us to be able to return to all the activities we did before 2020. We still need to continue doing everything we can to stay safe – like following public health guidelines restricting gatherings, practising physical distancing and wearing masks. However, by choosing to get vaccinated when the vaccines are available to you, you can protect yourself from getting ill from the coronavirus.

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