Vaccine Questions and Answers

The Canadian Press

A COVID-19 vaccine from Pfizer has arrived in Ontario and Quebec, with the first inoculations scheduled to happen on Monday morning in Toronto, Montreal, and Quebec City.

Canada is set to receive 249,000 doses of the drug from the U.S. pharmaceutical giant and its German partner BioNTech by the end of the month and four million total doses – enough to vaccinate two million people – by March.

Here’s what we know about today’s vaccinations and Pfizer’s product:

WHO IS GETTING VACCINATED FIRST?

Five front-line workers will be the first Ontarians to receive the vaccine at one of Toronto’s hospitals on Monday.

Ontario had 6,000 doses delivered over the weekend and plans to vaccinate approximately 2,500 more health-care workers. Each person who is vaccinated needs two doses 21 days apart.

In Quebec, residents of long-term care homes in Montreal and Quebec City will be the first to receive the shots, followed by staff.

HOW DOES THE VACCINE WORK?

Pfizer developed its vaccine with a novel technique of using messenger RNA (mRNA), which essentially teaches our cells how to make the coronavirus’s spike protein and trigger an immune response if we become infected with the virus in the future.

Pfizer’s vaccine uses a synthetically-produced mRNA that’s packaged in a fat, or lipid, coating. When injected into the arm muscle, the lipid hooks onto cells and dumps the mRNA there. It’s then translated into protein to make the antibody.

Another leading vaccine candidate from Moderna also uses mRNA. One from AstraZeneca uses a non-replicating viral vector – a virus that has been stripped of its genetic material and replaced with the spike protein gene of the coronavirus. That viral vector makes an mRNA molecule, and from there the protein and antibodies.

HOW EFFECTIVE IS IT?

Pfizer’s vaccine is 95 per cent effective in preventing SARS-CoV-2 infection beginning one week after the second dose, and Health Canada specifies on its website that people may not be protected against COVID-19 until at least seven days after the second dose.

The efficacy rate is based on studies in about 44,000 participants.

What’s not known is how long immunity lasts with any of the leading vaccine candidates.

WHAT ARE THE SIDE EFFECTS?

Health Canada says the side effects from Pfizer’s clinical trials were found to be “mild or moderate”’ and included things like pain at the site of injection, body chills and feeling tired and feverish.

The organization says those are common side effects of many 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,” the website says. “A serious side effect might be something like an allergic reaction.”

WHAT ARE THE HURDLES FACING DISTRIBUTION?

Pfizer’s vaccine, like Moderna’s and AstraZeneca’s, requires two doses injected roughly three weeks apart.

Tracking will become particularly important with a two-dose vaccine, to make sure people are going back to their doctor or pharmacy to get their second dose, and to ensure they’re receiving the right vaccine if more than one option is available.

Storage could also prove problematic with Pfizer’s product, which requires ultra-low freezers that can keep it at minus 70 C until a short time before it’s injected. Moderna’s needs a temperature around minus 20 C – about the same as a regular freezer.

Pfizer and Moderna need cooler temperatures for their vaccines because of the instability of the mRNA. AstraZeneca’s vaccine, meanwhile, can be stored in a fridge.

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