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

Sheriff Avory Chapman was last seen Jan. 20 on Wellington Avenue in Chilliwack. (RCMP)
RCMP look for missing man last seen in downtown Chilliwack

21-year-old Sheriff Avory Chapman has been missing since Jan. 20

A worker is seen throwing a chicken in an undercover video in 2017 filmed by California-based animal rights activists Mercy For Animals.
Fraser Valley chicken abuse trial delayed until February

Originally scheduled for a jury trial, Sofina and Chilliwack company now face judge alone

Recently elected NDP MLA Kelli Paddon is funding three $500 scholarships for students demonstrating a commitment to equity and social change. (Black Press file photo)
Chilliwack-Kent MLA Kelli Paddon funding Equity and Social Change Scholarships

One of the scholarships is open to any graduating student in the Chilliwack-Kent electoral district

Paid parking returns to Harrison from May 15 to Sept. 15. (Nina Grossman/The Observer)
Harrison pay parking to arrive May 15, parking master plan in the works

The village will be looking at parking for the community as a whole in the new plan

Crews with Discovery Channel film as an Aggressive Towing driver moves a Grumman S2F Tracker aircraft around a 90-degree turn from its compound and onto the road on Saturday, Jan. 23, 2021. It was the “most difficult” part of the move for the airplane, one organizer said. (Jenna Hauck/ Chilliwack Progress)
VIDEO: Vintage military plane towed across Chilliwack over weekend

Grumman CP-121 Tracker’s eventual home the British Columbia Aviation Museum on Vancouver Island

Rose Sawka, 91, waves to her son through the window of a care home in Prince Rupert in October. Residents of the care home received their first vaccine dose Jan. 20. (K-J Millar/The Northern View)
B.C. care home visitor access to expand by March, Dix says

Staff, residents, essential visitors top priorities for vaccine

The Independent Investigations Office of BC (IIO) is looking into the death of man discovered Jan. 11 in east Maple Ridge. (Black Press files)
B.C.’s police watchdog investigating man’s death in Maple Ridge

Man was found dead Jan. 11 after recent contact with police

Chilliwack Law Courts. (Black Press file)
Man sentenced to 20 months for sexual offences involving a minor in Mission

Will Laws Clark was 22 and victim was 13 at time offences began

Rolling seven-day average of cases by B.C. health authority to Jan. 21. Fraser Health in purple, Vancouver Coastal red, Interior Health orange, Northern Health green and Vancouver Island blue. (B.C. Centre for Disease Control)
2nd COVID vaccine doses on hold as B.C. delivery delayed again

New COVID-19 cases slowing in Fraser Health region

Provincial health officer Dr. Bonnie Henry talk about the next steps in B.C.’s COVID-19 Immunization Plan during a press conference at Legislature in Victoria, B.C., on Friday, January 22, 2021. Two more cases of the COVID-19 strain first identified in South Africa have been diagnosed in British Columbia, bringing the total to three as of Jan. 16.THE CANADIAN PRESS/Chad Hipolito
B.C. now has three cases of South African COVID-19 variant, six of U.K. strain

Both variants are thought to spread faster than earlier strains

Join Black Press Media and Do Some Good
Join Black Press Media and Do Some Good

Pay it Forward program supports local businesses in their community giving

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

Rodney and Ekaterina Baker in an undated photo from social media. The couple has been ticketed and charged under the Yukon’s <em>Civil Emergency Measures Act</em> for breaking isolation requirements in order to sneak into a vaccine clinic and receive Moderna vaccine doses in Beaver Creek. (Facebook/Submitted)
Great Canadian Gaming CEO resigns after being accused of sneaking into Yukon for vaccine

Rod Baker and Ekaterina Baker were charged with two CEMA violations each

Police discovered a makeshift nightclub in a Vancouver apartment on Jan. 23, 2021, and say it wasn’t the first time this month officers have been called to the unit over social gathering concerns. (Phil McLachlan - Capital News)
Doorman of makeshift ‘booze-can’ in Vancouver apartment fined; police look to court order

This marks the fourth complaint about social gatherings inside the apartment in January

Most Read