Comparing COVID-19 vaccines: What’s the difference between the Pfizer and the Moderna dose? - Toronto Star

Soon, there could be two.

Health Canada is expected to make a regulatory decision imminently on a second COVID-19 vaccine.

Prime Minister Justin Trudeau has said shipments of the American-developed Moderna vaccine candidate are waiting to be transported into this country if and when the green light is given.

The first fully tested vaccine, from Pfizer-BioNTech, rolled out to long-term-care residents and health-care workers this week. Trudeau has said that initial supply could be bolstered by as many as 168,000 Moderna doses before the end of the year.

The existence of more than one effective, authorized COVID-19 vaccine has long been anticipated.

Experts have said from the beginning that the hundreds of teams toiling away on COVID-19 vaccines were likely to produce not just one winner, but a portfolio of doses.

The use of each might shift as supplies ebb and flow, or if one or another proves to be particularly effective in a specific population.

Alan Bernstein, who is a member of Canada’s Vaccine Task Force, the group that advised the government as to which vaccines to buy, says these first two options use a similar technology and are fairly similar as a result, but that bigger differences could be discovered as they’re given to more people.

“I think what we can say is these both vaccines are amazingly effective at preventing disease,” said Bernstein, who is also the president and CEO of CIFAR, a Canadian-based global research organization.

Here’s what we know about them so far.

How do they work?

Both vaccines are built on a new technology that uses messenger ribonucleic acid (mRNA) to trick your body into making tiny copies of the coronavirus’s distinctive spike protein, which then teaches your immune system to fight off a future attack.

One of the major advantages of the technology is that you can make a vaccine very quickly, which is a major reason why these are expected to be the first two candidates to clear testing and gain regulatory approval.

There are other vaccine candidates still in trials that use other methods or “platforms” that might end up looking quite different.

For example, one might emerge as more effective for seniors or give longer immunity, which is when you might see health officials start to use certain doses for specific demographics, Bernstein says.

How are they given?

The Pfizer-BioNTech is 0.3-millilitre dose of a white-ish coloured liquid. Two shots are given 21 days apart.

The Moderna dose is also “white to off-white” but is 0.5 -millilitres. Two shots are given 28 days apart.

How well do they work?

Both vaccines have posted very high efficacy rates based on testing on thousands of people around the world.

Pfizer-BioNTech was found to be 95 per cent effective, and Moderna was 94.5 per cent effective. Those percentages were calculated by comparing the number of trial volunteers who got COVID-19 after having been vaccinated versus those who were part of the placebo group.

These are hugely impressive numbers for brand new vaccines, Bernstein notes.

“In the real world, you’re not going to get better than 95 per cent. There’s no way you’re going to get a vaccine that is so good that it can simply prevent disease completely.”

How are they transported?

This is the most significant difference between the two vaccines, Bernstein says.

The Pfizer-BioNTech is more challenging to transport — requiring temperatures between -70 and -80 C. Once it’s defrosted, it must be used relatively quickly.

The Moderna vials can be shipped at -20 C.

The difference is already affecting which regions are getting which vaccine. The territories passed on the Pfizer-BioNTech vaccine but are first in line if and when Moderna becomes available.

“If you think about Canada’s far North, if you think about Africa, if you think about small towns in Ontario or anywhere in Canada, they don’t all have a -70 C freezer to hold these things,” Bernstein says. “So there’s a huge difference in the cold-chain requirements.”

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He points out the AstraZeneca vaccine — which is in late-stage trials and has begun the Canadian regulatory process — can be shipped at 4 C, which would give it an advantage, should it prove successful.

How were they tested?

Pfizer-BioNTech has been tested on more than 44,000 people in Argentina, Brazil, Germany, South Africa, Turkey, Japan and the United States.

Moderna was tested on about 30,000 people in the U.S.

Who made them?

As the name suggests, Pfizer-BioNTech is a partnership between a German startup that specializes in mRNA technology and drug giant Pfizer.

Moderna Therapeutics is a U.S. company based in Cambridge, Mass., that also specializes in trying to use mRNA to make drugs.

Both doses have Canadian connections.

The lipid nanoparticles — which are like tiny protective jackets for the strands of mRNA — for the Pfizer-BioNTech dose are made in Vancouver by a company called Acuitas Therapeutics.

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Meanwhile, Moderna was co-founded by Derrick Rossi, a Toronto-born stem cell biologist.

Do they work better on some people than others?

Data from human trials suggest both doses are slightly more effective in males than females and also had a slight edge in people with other conditions, such as diabetes and cardiac disease.

But Bernstein cautions that the differences at this point are slight, and that more information will be collected as the vaccines are rolled out to more people.

What don’t we know about them?

Both vaccines were tested to see if they could prevent COVID-19 in a person exposed to the coronavirus.

What’s not clear yet — but will be, given some time, Bernstein says — is whether or not a vaccinated person could still carry the virus in their upper respiratory tract and cough it onto other, unvaccinated people.

It’s also not known yet how long vaccination will last.

How much should you care which vaccine you’re given?

Right now, there isn’t enough of a difference in the vaccines to really care which one you get, Bernstein says.

“They’re pretty similar, if not identical, in all practical regards that we know of now,” he says, though that might change as more people take them and more results become available.

“Speaking personally, I’ll take the first one I’m offered.”

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2020-12-17 11:01:33Z
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