This undated photo issued by the University of Oxford shows of vial of coronavirus vaccine developed by AstraZeneca and Oxford University, in Oxford, England. Pharmaceutical company AstraZeneca said Monday Nov. 23, 2020, that late-stage trials showed its coronavirus vaccine was up to 90% effective, giving public health officials hope they may soon have access to a vaccine that is cheaper and easier to distribute than some of its rivals. (University of Oxford/John Cairns via AP)

This undated photo issued by the University of Oxford shows of vial of coronavirus vaccine developed by AstraZeneca and Oxford University, in Oxford, England. Pharmaceutical company AstraZeneca said Monday Nov. 23, 2020, that late-stage trials showed its coronavirus vaccine was up to 90% effective, giving public health officials hope they may soon have access to a vaccine that is cheaper and easier to distribute than some of its rivals. (University of Oxford/John Cairns via AP)

VIDEO: How do the leading COVID vaccines differ? And what does that mean for Canada?

All three of the drug companies are incorporating novel techniques in developing their vaccines

On Monday AstraZeneca became the third pharmaceutical company this month to announce promising results from a late-stage coronavirus vaccine clinical trial, joining Pfizer and Moderna as the leading candidates for developing an effective prevention for COVID-19.

While all promise a suitable vaccine can be rolled out within the coming months, they differ slightly in efficacy, delivery and other components.

So how do we judge the leading candidates so far, and how might they impact a vaccine rollout program in Canada?

The Canadian Press asked Kelly Grindrod, an associate professor at the University of Waterloo’s School of Pharmacy, and Dr. Earl Brown, a virology and microbiology expert at the University of Ottawa, to break down those questions.

HOW DO THEY WORK?

All three of the drug companies are incorporating novel techniques in developing their vaccines, with Pfizer and Moderna using messenger RNA (mRNA) and AstraZeneca using a non-replicating viral vector.

AstraZeneca’s vaccine, developed with Oxford University, takes a chimpanzee cold virus that’s not harmful to humans and “hides” pieces of the coronavirus in it, Grindrod explained. Non-replicating means the virus won’t actually reproduce throughout the body.

“It shows our cells how to make the coronavirus spike protein so that our bodies can actually have an immune response to it,” she said.

Brown explained it as a “dummy virus” that has essentially had its genes stripped and replaced with the spike protein gene for the coronavirus. The vaccine makes an mRNA molecule from the genome and that molecule makes the protein, he said.

“The protein is put on the cell, the immune system recognizes it and makes antibodies — therefore immunity.”

The mRNA vaccines are similar, but structurally different with Brown simplifying it by saying Pfizer and Moderna “put the RNA right into your arm.”

“Their vaccine is a synthetically-produced mRNA packaged in a fat coating,” he said. “So they inject that into your muscles, that little fat gloms onto your cells, fuses with them and becomes part of the cell and dumps that mRNA into your cell. And then the mRNA is translated into protein.”

Grindrod said both vaccine methods “show us the genetic component” our cells need to make the antibodies.

“It’s just really how it’s delivered,” she added.

HOW EFFECTIVE ARE THEY?

AstraZeneca says its vaccine was up to 90 per cent effective when a half dose was followed by a full dose a month later. Another method, where two full doses were distributed a month apart, showed to be 62 per cent effective.

Moderna said last week that preliminary data showed a 94.5 per cent efficacy, and Pfizer, the first to share its initial results earlier this month, upped theirs from 90 to 95 after releasing final trial results last week.

While the medical journal “The Lancet” did review some of AstraZeneca’s results, Grindrod says to remember that most of the efficacy claims from the clinical trials are from press releases based off preliminary data.

“Now what we’re waiting for is the actual study, the full published, peer review that you can see and compare efficacy and safety and how they measured it,” she said, adding she expects peer-reviewed studies on the vaccines to emerge soon.

“Things are coming at much different timelines than we’re used to.”

Another factor that’s still unknown is how long immunity lasts, and whether we will need booster vaccines in the future.

WHAT ARE THE HURDLES FACING DISTRIBUTION?

All three of the leading vaccine candidates require two doses, injected roughly one month apart, and there could be challenges in getting people back to a doctor or pharmacy to receive their second dose.

Grindrod said tracking will become particularly important with a two-dose vaccine, especially if AstraZeneca goes forward with injecting different amounts of the vaccine per dose. Rollout can become even more complicated when there’s a surge for the vaccine, as we saw this year with the flu shot.

“You have to track who got which vaccine, which dose, and make sure they come back three to four weeks later,” she said.

Where AstraZeneca could have the upper hand in distribution, however, is in its storage temperature. The company says its vaccine can be stored in a fridge, unlike Moderna and Pfizer, which require freezing temperatures due to the instability of the mRNA, Brown says.

Pfizer’s vaccine needs to be stored at minus-70 C, while Moderna’s needs a temperature around minus-20 C — about the same as a regular freezer.

“For really ultra-low temperature freezers, you find those in hospitals and research laboratories, but not many other places,” Brown said. “So we aren’t prepared for (a vaccine that requires) ultra low freezers.”

READ MORE: 3rd major COVID-19 vaccine shown to be effective and cheaper

ARE THERE ANY SIDE EFFECTS?

Side effects for all three vaccines have been minimal — things like sore arms, fatigue and headaches that generally don’t last long — and Brown says the presence of those reactions are a good thing.

“When you’re vaccinating, you’re stimulating an immune response, and those are immune-regulated things,” he said. “So a sore arm reaction is good, because that means it’s working for you.”

More safety data, which can only be garnered from monitoring trial participants over a longer term, is needed to judge further, he says.

WHAT’S NEXT, AND WHAT DOES IT MEAN FOR CANADA?

The Food and Drug Administration (FDA) is meeting to discuss Pfizer’s emergency use authorization request on Dec. 10, which means a vaccine rollout could happen in the United States within the next month.

But the vaccines would need approval from Health Canada in order to get them here.

Health Canada’s website says it will review authorization submissions from companies to determine “evidence of safety, efficacy and manufacturing quality for each vaccine.”

Canada locked in a supply of potential vaccine candidates when it signed agreements with a number of pharmaceutical companies, including AstraZeneca, Pfizer and Moderna months ago, and that should accelerate a rollout when ready.

READ MORE: First COVID vaccines could arrive in U.S. on Dec. 12

But the actual time frame will depend on when these drug companies can show enough safety data to move forward, Brown said.

Grindrod expects a viable candidate to be approved quickly after safety and efficacy can be shown.

“We might see early 2021 and it’s not clear whether that’s January or February or around that time,” she said. “From there, as we get more doses and more vaccines are approved, then we may see a broader population getting vaccinated. But it’s hard to say when that will happen.”

Melissa Couto Zuber, The Canadian Press


Like us on Facebook and follow us on Twitter.

Want to support local journalism during the pandemic? Make a donation here.

Coronavirusvideo

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

A health-care worker prepares a dose of the Pfizer-BioNTech COVID-19 vaccine at a UHN COVID-19 vaccine clinic January 7, 2021. THE CANADIAN PRESS/Nathan Denette
Employers might be able to require COVID-19 vaccination from employees: B.C. lawyer

‘An employer must make the case’ using expert science, explains lawyer David Mardiros

On Aug. 26, 1947, a fire sparked in the lumber piles between Alberni Pacific Division sawmill and Alberni Plywood (located where Canal Waterfront Park is now). What resulted was a huge fire on Assembly Wharf One, where several buildings were gutted and stacks of lumber were burned. This photo is one of 24,000 contained in the Alberni Valley Museum’s digital archives, at https://portalberni.pastperfectonline.com. (PHOTO PN07386 COURTESY ALBERNI VALLEY MUSEUM)
LOOK BACK: 1947 fire destroys Port Alberni wharf

Take a peek into the Alberni Valley’s history with the Alberni Valley Museum

Artist Jim Holyoak’s installation “Quagmire.” Holyoak will be the first speaker for the Artist Talk Online Winter 2021 series. (SUBMITTED PHOTO)
North Island College Artist Talk goes online for winter 2021

The series invites contemporary Canadian artists to speak about their professional practice

(NEWS FILE PHOTO)
City of Port Alberni, ACRD prepare for compost collection in 2021

Roadside pickup is expected to begin in the City of Port Alberni in June 2021

U.S. Senator Bernie Sanders sits in on a COVID-19 briefing with Dr. Bonnie Henry, provincial health officer, and Adrian Dix, B.C. minister of health. (Birinder Narang/Twitter)
PHOTOS: Bernie Sanders visits B.C. landmarks through the magic of photo editing

Residents jump on viral trend of photoshopping U.S. senator into images

A woman injects herself with crack cocaine at a supervised consumption site Friday, Jan. 22, 2021 in Ottawa. THE CANADIAN PRESS/Adrian Wyld
Drug users at greater risk of dying as services scale back in second wave of COVID-19

It pins the blame largely on a lack of supports, a corrupted drug supply

Wet’suwet’en supporters and Coastal GasLink opponents continue to protest outside the B.C. Legislature in Victoria, B.C., on Thursday, February 27, 2020. THE CANADIAN PRESS/Chad Hipolito
‘We’re still in it’: Wet’suwet’en push forward on rights recognition

The 670-km Coastal GasLink pipeline was approved by B.C. and 20 elected First Nations councils on its path

The sky above Mt. Benson in Nanaimo is illuminated by flares as search and rescuers help an injured hiker down the mountain to a waiting ambulance. (Photo courtesy Nanaimo Search and Rescue)
Search plane lights up Nanaimo mountain with flares during icy rope rescue

Rescuers got injured hiker down Mt. Benson to a waiting ambulance Saturday night

Jennifer Cochrane, a Public Health Nurse with Prairie Mountain Health in Virden, administers the COVID-19 vaccine to Robert Farquhar with Westman Regional Laboratory, during the first day of immunizations at the Brandon COVID-19 vaccination supersite in Brandon, Man., on Monday, January 18, 2021. THE CANADIAN PRESS/Tim Smith - POOL
Top doctor urges Canadians to keep up with COVID measures, even as vaccines roll out

More than 776,606 vaccines have been administered so far

Cannabis bought in British Columbia (Ashley Wadhwani/Black Press Media)
Is it time to start thinking about greener ways to package cannabis?

Packaging suppliers are still figuring eco-friendly and affordable packaging options that fit the mandates of Cannabis Regulations

From the left: Midway RCMP Csts. Jonathan Stermscheg and Chris Hansen, Public Servant Leanne Mclaren and Cpl. Phil Peters. Pictured in the front are Mclaren’s dog, Lincoln and Peters’ dog, Angel. Photo courtesy of BC RCMP
B.C. Mounties commended for bringing firewood to elderly woman

Cpl. Phil Peters said he and detachment members acted after the woman’s husband went to hospital

Dr. Jerome Leis and Dr. Lynfa Stroud are pictured at Sunnybrook Hospital in Toronto on Thursday, January 21, 2021.THE CANADIAN PRESS/Frank Gunn
‘It wasn’t called COVID at the time:’ One year since Canada’s first COVID-19 case

The 56-year-old man was admitted to Toronto’s Sunnybrook Health Sciences Centre

An Uber driver’s vehicle is seen after the company launched service, in Vancouver, Friday, Jan. 24, 2020. Several taxi companies have lost a court bid to run Uber and Lyft off the road in British Columbia. THE CANADIAN PRESS/Darryl Dyck
Taxi companies lose court bid to quash Uber, Lyft approvals in British Columbia

Uber said in a statement that the ruling of the justice is clear and speaks for itself

Most Read