What you need to know as we get closer to a COVID-19 vaccine

This week's edition ofSecond Opinion is a collaboration with CBC's The Dose podcast, hosted by Dr. Brian Goldman.

As more regions of Canada enter lockdownand increaserestrictionsin an effort to contain the alarming spread of COVID-19, many government and public health officials are pointing to two promisingcoronavirus vaccine candidates as hope that the pandemic will one day end.

Over the last week, both Pfizer and Moderna Inc. announced that their respective vaccines appeared to be 95 per cent effective in Phase 3 clinical trials. They are two of the seven manufacturers with whom Canadahas signed purchasing deals for millions of doseseach.

Dr. Howard Njoo, the country's deputy chief public health officer, has said that if the vaccines are approved by Health Canada, he's hopeful that the majority of Canadians could be vaccinated by the end of 2021.

But amid the optimism, a new vaccinenaturally raises lots of questions, from how it works towho will get it first in a country of more than 35million people.

Here are some answers to those questions.

The two front-running vaccines use a new technology called mRNA.What is that?

Traditionally, vaccines have been made using either dead or"live attenuated" or weakenedviruses to provoke an immune response in the body.

Both Pfizer'sand Moderna's vaccines use pieces of genetic material messenger RNA (mRNA)from the coronavirus that causes COVID-19.This new technologyhas never been used before in commercial vaccines, said Dr. Jeff Kwong, interim director at the University of Toronto's Centre for Vaccine Preventable Diseases.

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"It actually gets your body's cells to produce the proteins or antigens of the virus and then that stimulates the immune response," he told Dr. Brian Goldman, host of the CBC podcast The Dose.

"So we're not actually giving the virus to people, but we're just giving the genetic material of the virus so that we will generate the antigens that will train our immune system to fight off the virus."

The reason the mRNA vaccine results are coming out faster thanmore than 150 other coronavirus vaccine trials invarious stages of development around the world,Kwong said, is because "it's much more efficient" to inject the mRNA directly into the body than to produce antigens by injecting particles of virus into eggs or cells first. That's the more traditional method used by many other vaccine manufacturers.

Some social media postsclaim that mRNA vaccines can damage or change a person's own DNA is that true?

Absolutely not.That's misinformation, Kwong said.

First of all, the mRNA vaccinedoesn't enter the nucleus of cells, where most DNA is located.

"It doesn't affect our own genetic material.It's just taking advantage of our own body's machinery to generate the antigens," he said. "So it's kind of like borrowing our cells to manufacture the antigens instead of making the antigens in cells or in eggs and then injecting that into the body."

What are the steps between now and getting vaccinated against COVID-19?

Although very promising, the results are still preliminary, Kwong cautions. Here's what needs to happen:

1. Phase 3 of the clinical trials needs to be completed.

2. The data from the trials need to be reviewed by the regulator for each country here, that's Health Canadato independently ensure that the vaccine is both safe and effective.

3. If Health Canada approves the vaccine, the manufacturer needs to ship the doses to Canada, where it will be distributed to the provinces and territories.

4. It's then up to the provinces and territories to follow their rollout plan, which they should be developing now, to get the vaccine to public health authorities, physicians' offices, hospitals, long-term care homes, pharmacies, or wherever the vaccines are to be given to people who want one.

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How many doses of vaccine will we need in Canada?

Both the Pfizer and Moderna vaccines require two doses, taken three weeks apart.It's likely that other successful vaccine candidates may also require multiple doses, experts say.With a population of more than 35 million people in Canada, that means more than 70 million doses in total.

Although the agreements Canada has signed with manufacturers more than covers that amount, they won't all arrive at once.They're likely to come in staggered shipments throughout 2021 as they're made, Kwong said.

Then who gets vaccinated first?

The National Advisory Committee on Immunization (NACI), an independentbody that advises thePublic HealthAgency of Canada, recently published "preliminary guidance"on how to prioritize immunization against COVID-19 once a vaccine is approved.

According to NACI, the first vaccines should go to:

• People at high risk of death or severe illness from COVID-19 (including seniors and people who have high-risk health conditions).
• People who are most likely to transmit COVID-19 to those at high risk (this could include health-care workers,support workers or people living with those at high risk).
• Workers essential to maintaining the COVID-19 response or providing frontline care for COVID-19 patients.
• People"contributingto the maintenance of other essential services for the functioning of society." These workers still need to be defined in discussions between the federal, provincial and territorial governments, NACI said, but could include police, firefighters or grocery store staff.
• People living or working in conditions that put them at higher risk of infection, or where infection could have "disproportionate consequences, including Indigenous communities."

What about children?

On Nov. 17, the American Academy of Pediatrics issued a news release calling for children to be included in COVID-19 vaccine clinical trials immediatelyto ensure that they "are notleft out of potentially life-saving vaccines."

Pfizer "only recently" began enrolling children as young as 12, the academy said.

"Children are not little adults. We must include children in the trials as soon as it is safe to do so," said Dr. Yvonne Maldonado, chair of the academy's committee on infectious diseases, in the release.

"This research takes time. If this does not begin soon, it will be less likely a vaccine will be available for children before the next school year."

CBC News contacted the Canadian Paediatric Society for comment, but they were not able to respond by deadline.

However, both Kwong and Dr. Jeffrey Pernica, head of the division of pediatric infectious disease at McMaster University, agreed with the American organization's position.

"COVID-19 only rarely causes severe disease in children but there have been significant impacts on child and youth health from the pandemic," Pernica said in an email to CBC News.

"If we want to develop real herd immunity, we'll have to immunize kids as well," Pernica said. "We absolutely have to have data on whether they are safe and effective in children.

"Amajority of parents will probably not wish to immunize their children with vaccine products that have not been verified to be safe in that age group."

What are the logistical challenges in getting the vaccines to Canadians?

The number one challenge, Kwong said, is the sheer volume of the supply needed.

"The hope is that we can get everyone who wants to get vaccinated as quickly as possible," he said.

Once the supply arrives, Kwong believes that between physicians, public health nurses and pharmacists (in provinces where they are allowed to provide vaccinations), there will be enough people to give the vaccination over the course of 2021.Military support would be "welcome assistance," he said particularly in helping the vaccine reach remote areas.

A key challenge with the Pfizer vaccine, however, is that it needs to be kept at -70 C a temperature far colder than what's possible in most freezers.(Moderna has said its vaccine can be kept in a refrigerator for up to a month.)

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The Public Health Agency of Canada is in the process of making sure the need for ultra-freezers doesn't hold up the vaccination process, spokesperson Eric Morrissettesaid.

The agency is working with the provinces and territories to review where equipment currently exists including "the ability to safely transport and store ultra-low temperature and frozen vaccines," Morrissette said in an email on Friday.

"Any capacity gaps will be addressed to ensure the safe and timely delivery of vaccines." he said.

Once we're vaccinated, will we be immune to COVID-19 for life?

That's still unknown, Kwong said, because it's been less than a year since the virus appeared on anyone's radar. Although the clinical trialsshowed a high rate of achieving immunity, there's really no way to know how long it lasts until people are vaccinated in the real world and more time passes.

"There are many vaccines that offer essentially lifelong protection, and some that don't,"Dr. Lynora Saxinger, an infectious diseases specialist at the University of Alberta, told CBC News in an email.

However, Saxinger is encouraged by the messenger RNA technology in the Pfizer and Moderna vaccines.

"mRNA vaccines basically are designed to give your own cells a code to make the virus spike protein so your immune system really sees it in a way that mimics natural infection," she said. "This should increase the likelihood of a good long-term response."

Even ifit doesn't,multiple doses over the years are sometimes required in existing vaccines.A booster shot is neededevery 10 years for tetanus, for example. The flu vaccine requires a shot every year.

"One nice thing about vaccines is that booster strategies can be used if it doesn't prove to have a long-lasting effect." Saxinger said.

Plus, more vaccine candidates of different types are expected to prove successful in the coming months, she said, and some may prove to be more effective in certain people than others.

"It's good to have a menu to choose from," Saxinger said.

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