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

As of Friday, Alberta has under 10,000 active COVID-19 cases. (Image courtesy CDC)
Alberta identifies 573 new COVID-19 cases, 13 deaths on Saturday

There are currently 9,727 active cases of the virus in the province

As of Friday, Alberta has under 10,000 active COVID-19 cases. (Image courtesy CDC)
Three new COVID-19 deaths in Central zone, Alberta under 10,000 active cases

The Central zone sits at 849 active cases, with 52 people in hospital and 10 in the ICU.

Alberta’s chief medical officer of health Dr. Deena Hinshaw announced 16 additional deaths Thursday. (Photo by Chris Schwarz/Government of Alberta)
No easing of Alberta’s COVID-19 measures Thursday, 678 new COVID-19 cases

The province also hit 1,500 COVID-19 deaths since the beginning of the pandemic

Dean Olsen Missing Poster
Blackfalds RCMP seek public assistance to locate missing male

Dean Olsen was last seen on Jan. 20 in Red Deer County

Alberta Premier Jason Kenney said the Canadian government should consider sanctions on the U.S. if they refuse to reconsider the decision to cancel the Keystone XL Pipeline. (THE CANADIAN PRESS/Sean Kilpatrick
Keystone XL officially cancelled, Kenney vows to fight on

U.S. President Joe Biden cancelled the presidential permit for the pipeline on first day of office

Alberta’s chief medical officer of health, Dr. Deena Hinshaw, updates media on the COVID-19 situation in Edmonton, Friday, March 20, 2020. Hinshaw says residents in long-term care and supportive living facilities will remain the priority as the province grapples with a looming slowdown in COVID-19 vaccine supply. THE CANADIAN PRESS/Jason Franson
Alberta long-term care residents remain priority in looming slowdown of COVID vaccine

There are 119 patients in intensive care and 1,463 people have died

FILE - In this Feb. 14, 2017, file photo, Oklahoma State Rep. Justin Humphrey prepares to speak at the State Capitol in Oklahoma City. A mythical, ape-like creature that has captured the imagination of adventurers for decades has now become the target of Rep. Justin Humphrey. Humphrey, a Republican House member has introduced a bill that would create a Bigfoot hunting season, He says issuing a state hunting license and tag could help boost tourism. (Steve Gooch/The Oklahoman via AP, File)
Oklahoma lawmaker proposes ‘Bigfoot’ hunting season

A Republican House member has introduced a bill that would create a Bigfoot hunting season

FILE - In this Nov. 20, 2017, file photo, Larry King attends the 45th International Emmy Awards at the New York Hilton, in New York. Former CNN talk show host King has been hospitalized with COVID-19 for more than a week, the news channel reported Saturday, Jan. 2, 2021. CNN reported the 87-year-old King contracted the coronavirus and was undergoing treatment at Cedars-Sinai Medical Center in Los Angeles. (Photo by Andy Kropa/Invision/AP, File)
Larry King, broadcasting giant for half-century, dies at 87

King conducted an estimated 50,000 on-air interviews

Black Press File Photo
Maskwacis RCMP lay charges for attempted murder, kidnapping, and flight from police

Female victim remains in hospital in serious condition.

In this Dec. 18, 2020 photo, pipes to be used for the Keystone XL pipeline are stored in a field near Dorchester, Neb.  THE CANADIAN PRESS/AP-Chris Machian /Omaha World-Herald via AP
‘Gut punch’: Alberta Premier Jason Kenney blasts Biden on revoked Keystone XL permit

Kenney said he was upset the U.S. wouldn’t consult with Canada first before acting

Joe Biden, then the U.S. vice-president, and Prime Minister Justin Trudeau take their seats at the start of the First Ministers and National Indigenous Leaders meeting in Ottawa, Friday, Dec. 9, 2016. THE CANADIAN PRESS/Adrian Wyld
Trudeau, Biden to talk today as death of Keystone XL reverberates in Canada

President Joe Biden opposed the Keystone XL expansion as vice-president under Barack Obama

Prince Edward Island’s provincial flag flies on a flag pole in Ottawa, Friday July 3, 2020. A lozenge plant in Prince Edward Island has laid off 30 workers, citing an “almost non-existent” cold and cough season amid COVID-19 restrictions. THE CANADIAN PRESS/Adrian Wyld
‘Almost non-existent’ cold and cough season: P.E.I. lozenge plant lays off 30 workers

The apparent drop in winter colds across the country seems to have weakened demand for medicine and natural remedies

Gov. Gen. Julie Payette takes the royal salute from the Guard of Honour as she makes her way deliver the the throne speech, Wednesday, September 23, 2020 in Ottawa. THE CANADIAN PRESS/Fred Chartrand
Gov. Gen. Julie Payette resigns, apologizes for ‘tensions’ at Rideau Hall

Payette, who is the Queen’s representative in Canada, has been the governor general since 2017

Grounded WestJet Boeing 737 Max aircraft are shown at the airline’s facilities in Calgary, Alta., Tuesday, May 7, 2019. WestJet will operate the first commercial Boeing 737 Max flight in Canada today since the aircraft was grounded in 2019 following two deadly crashes. THE CANADIAN PRESS/Jeff McIntosh
Passengers unfazed as WestJet returns Boeing 737 Max to service on Calgary flight

After a lengthy review process, Transport Canada cleared the plane to return to Canadian airspace

Most Read