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

The Esquimalt Fire Department was called to a residence on Glengarry Place Monday afternoon for a fire that has displaced two families. There were no injuries and damage is being assessed. (Black Press Media file photo)
Esquimalt fire displaces two families as damage assessed

Fire broke out late Monday afternoon at residence on Glengarry Place

Former University of Victoria rowing coach Barney Williams is photographed in the stands during the Greater Victoria Invitational at CARSA Performance Gym at the University of Victoria in Victoria, B.C., on Friday, November 29, 2019. THE CANADIAN PRESS/Chad Hipolito
Rowing Canada sanctions former head coach of UVic varsity women’s team

Suspension of Barney Williams would be reversed if he complies with certain terms

A total of 10 flight exposures have affected the Victoria International Airport in April so far, making it the highest monthly total since the start of the pandemic. (Black Press Media file photo)
Victoria hits record-breaking number of monthly COVID-19 flight exposures

As of April 21, 10 flight exposures reported for the month

A new round of COVID-19 exposures has been reported at Dunsmuir Middle School, with potential exposure dates on April 7 to 15. (Google Streetview/Screenshot)
New COVID-19 exposures reported at Colwood middle school

People may bave been exposed on April 7 to 15

Victoria police are searching for Andrew Swanson who was last seen in Victoria April 7 and is wanted on warrants for choking and obstructing police. (Courtesy of VicPD)
Victoria police searching for missing man wanted for choking police

Andrew Swanson, 47, last seen in Victoria April 7

A lone traveler enters the Calgary Airport in Calgary, Alta., Monday, Feb. 22, 2021. THE CANADIAN PRESS/Jeff McIntosh
VIDEO: Trudeau defends Canada’s travel restrictions as effective but open to doing more

Trudeau said quarantine hotels for international air travellers will continue until at least May 21

In this image from video, former Minneapolis police Officer Derek Chauvin, center, is taken into custody as his attorney, Eric Nelson, left, looks on, after the verdicts were read at Chauvin’s trial for the 2020 death of George Floyd, Tuesday, April 20, 2021, at the Hennepin County Courthouse in Minneapolis, Minn. THE CANADIAN PRESS/Court TV via AP, Pool
George Floyd’s death was ‘wake-up call’ about systemic racism: Trudeau

Derek Chauvin was found guilty Tuesday on all three charges against him

A man pauses at a coffin after carrying it during a memorial march to remember victims of overdose deaths in Vancouver. THE CANADIAN PRESS/Darryl Dyck
B.C. announces historic half-billion-dollar funding for overdose crisis, mental health

Of it, $152 million will be used to address the opioid crisis and see the creation of 195 new substance use treatment beds

Children’s backpacks and shoes are seen at a CEFA (Core Education and Fine Arts) Early Learning daycare franchise, in Langley, B.C., on Tuesday May 29, 2018. THE CANADIAN PRESS/Darryl Dyck
B.C. budget to expand $10-a-day child care, but misses the mark on ‘truly universal’ system

$111 million will be used to fund 3,750 new $10-a-day spaces though 75 additional ChildCareBC universal prototype sites over the next three years.

Mak Parhar speaks at an anti-mask rally outside the Vancouver Art Gallery on Sunday, Nov. 1, 2020. Parhar was arrested on Nov. 2 and charged with allegedly violating the Quarantine Act after returning from a Flat Earth conference held in Geenville, South Carolina on Oct. 24. (Flat Earth Focker/YouTube.com screenshot)
Judge tosses lawsuit of B.C. COVID-denier who broke quarantine after Flat Earth conference

Mak Parhar accused gov, police of trespass, malfeasance, extortion, terrorism, kidnapping and fraud

Ambulance paramedic in full protective gear works outside Lion’s Gate Hospital, March 23, 2020. Hospitals are seeing record numbers of COVID-19 patients more than a year into the pandemic. (The Canadian Press)
B.C.’s COVID-19 infection rate declines, 849 cases Tuesday

Up to 456 people now in hospital, 148 in intensive care

Christy Clark, who was premier from 2011 to 2017, is the first of several present and past politicians to appear this month before the Cullen Commission, which is investigating the causes and impact of B.C.’s money-laundering problem over the past decade. (Darryl Dyck/Canadian Press)
Christy Clark says she first learned of money-laundering spike in 2015

The former B.C. premier testified Tuesday she was concerned the problem was ‘apparently at an all-time high’

Most Read