After approving the Pfizer-BioNTech COVID-19 mRNA vaccine on Wednesday, Health Canada shared information about how it works and any possible side effects on its website.
The vaccine is approved for people who are 16 years of age and older as its safety and effectiveness in younger people have not yet been established, the regulatory health body notes.
How it works
mRNA vaccines teach our cells how to make a protein that will trigger an immune response without using the live virus that causes COVID-19, explains Health Canada. Once triggered, our body then makes antibodies. These antibodies protect us from being infected if the real virus does enter our body in the future.
‘RNA’ stands for ribonucleic acid, which is a molecule that provides cells with instructions for making proteins. Messenger RNA (mRNA) vaccines contain the genetic instructions for making the SARS-CoV-2 spike protein. This protein is found on the surface of the virus that causes COVID-19.
When a person is given the vaccine, their cells will read the genetic instructions like a recipe and produce the spike protein. After the protein piece is made, the cell breaks down the instructions and gets rid of them.
The cell then displays the protein piece on its surface. Our immune system recognizes that the protein doesn’t belong there and begins building an immune response and making antibodies.
How it’s given
The vaccine is given by an injection (0.3 mL) into the muscle of the arm. For the vaccine to work best, an individual needs to get 2 doses: a single dose and then a second dose 21 days later.
Based on studies in about 44,000 participants, the Pfizer-BioNTech COVID-19 vaccine was 95% effective in preventing SARS-CoV2 infection beginning 1 week after the second dose. This means that people may not be protected against COVID-19 disease until at least 7 days after the second dose, says Health Canada.
Possible side effects
In general, the side effects observed during the clinical trials are similar to what you might have with other vaccines, Health Canada says on its information page about the Pfizer vaccine.
The side effects that followed vaccine administration in clinical trials were mild or moderate. They included things like pain at the site of injection, body chills, feeling tired and feeling feverish.
These are common side effects of vaccines and do not pose a risk to health.
As with all vaccines, there’s a chance that there will be a serious side effect, but these are rare. A serious side effect might be something like an allergic reaction.
Health Canada says it has conducted a rigorous scientific review of the available medical evidence to assess the safety of the Pfizer-BioNTech COVID-19 vaccine. “No major safety concerns have been identified in the data that we reviewed,” it assures Canadians adding that it “will monitor for any adverse events that may develop after immunization”.
Once the product is on the market, the manufacturer (Pfizer Canada ULC and BioNTech Manufacturing GmbH) is legally required to submit reports of adverse events to Health Canada.
The manufacturer is planning to follow clinical trial participants for at least 2 years after the second dose of the vaccine is given. It must communicate any potential safety concerns to Health Canada.
