VANCOUVER—Darren Campbell wouldn’t wish COVID-19 on anyone. Having lived through it, he knows the horrors of the disease better than most.

At Campbell’s low point with the coronavirus in late March, the 43-year-old from Ottawa was in the intensive-care unit, struggling to breathe and wondering how it had become so bad.

“I really thought: There’s a chance I might not get through this,” he said. “When someone says, ‘We’ve got to move you to the ICU’ — it kind of freaked me out.”

Now that he’s recovered, there’s another idea that Campbell finds concerning: Before Canada’s COVID-19 pandemic can end, more people will have to get sick with the disease that threatened his life.

That’s because the only way to beat COVID-19 is for a massive part of the population to become immune to the virus.

Scientists and public health officials agree that the best road to mass immunity is an effective vaccine, which is likely a year or more away. In the meantime, public health officials are grappling with how and when to reopen parts of society, with B.C. on Friday announcing the first steps in its plan.

Since the virus is already in the community, this involves deciding who can most safely be exposed, and under what circumstances, without unduly risking lives and instigating major outbreaks that overwhelm the health-care system. There’s another consideration, too: Scientists believe those who get sick and recover will be immune, which would help to slow the spread of the disease.

So who are the best candidates to wade into the coronavirus fire?

It’s believed that Campbell and others who have recovered are about as low risk for contracting and passing on the coronavirus as it’s possible to be. Having had COVID-19, their bodies have developed “antibodies” adept at fighting it off — like blood-protein foot soldiers trained in the absolute defeat of a particular deadly foe.

If COVID-19 acts like SARS, scientists expect that those who recover from it will stay immune — they won’t get the virus again or pass it on. And if enough people are immune, the virus will spread more slowly, and it will die out. A Harvard epidemiologist has estimated that COVID-19 could be beaten if half the world’s population were immune.

But not all forms of immunity are equal.

“Getting immunity from infection is not optimal and it will happen over a longer period of time,” B.C. provincial health officer Dr. Bonnie Henry said Friday. “Our goal is to control the transmission and growth of COVID-19 cases while continuing to monitor and minimize the unintended negative consequences of (public health) measures.”

She said teams of public health professionals are contemplating a variety of strategies to gradually reopen society and the economy, and that they haven’t yet landed on exactly what measures will be lifted and when.

Businesses that are able to maintain social distancing could open again, Henry suggested, and workplaces and schools may begin running on rotating schedules that allow participants to keep their distance from one another.

As case numbers in B.C. decline, the province is contemplating loosening these restrictions even as cases continue to grow elsewhere — especially Ontario and Quebec.

But there are signs that the growth of the disease even in Ontario and Quebec may be levelling off, raising questions about how each jurisdiction will tackle who will be allowed to interact and when.

Dr. Greg Poland, a professor of medicine and an immunology expert with the Mayo Clinic in Rochester, Minn., imagines the easing of COVID-19 restrictions like a “target”: You start by opening up society for the people inside the bullseye, and progress slowly to opening up the concentric circles around the bullseye, monitoring the situation over several incubation periods to make sure the virus doesn’t spread too quickly.

“The bullseye, the easiest one, is people who have already been infected,” he said. That’s because scientists expect they are immune. “The next ring is people whose risk factors are the lowest, pretty much people up to age 30 or so.”

From there, Poland said, the task of public health officials would be to allow certain groups of people to gather in limited contexts. Perhaps young adult workers can be together in offices, or cafes can begin serving at tables spaced apart — the specifics haven’t yet been determined.

Scientists and health officials would observe what happens beyond the two-week incubation period, then decide whether to tighten restrictions again, or open up a bit more and repeat the cycle.

“It’s almost the canary in the mine,” Poland said. “Who can you afford to put in the mine? Probably schoolchildren, because the chance of communicating the disease is low.”

Photos of Denmark this week showed Prime Minister Mette Frederiksen speaking to a class of children with desks spaced two metres apart. Parents formed now familiar social distancing lines to drop their kids off at school, and yoga classes were conducted in parks, with participants spaced several arm lengths apart.

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Poland said that if infection rates remain low after those “bullseye” groups return to interacting with one another, health officials could reintroduce young, healthy adults to work as a next step. The most vulnerable — the elderly and immunocompromised — would likely stay isolated the longest.

B.C.’s Henry has spoken about a similar concept as a “roller-coaster,” suggesting that when the province does start lifting restrictions, it may not do so in a straight line.

The hope is that building a ring of people within a population who are immune to COVID-19 could help protect the most vulnerable, too, because the virus will have fewer bodies available to infect and spread.

“You’re trying to create herd immunity by having people slowly develop the disease,” said Andrew Shih, the medical director of transfusion medicine at Vancouver Coastal Health.

“Once people have the immunity, they by-and-large protect the more immunocompromised and (people at) higher risk.”

Poland sees the introduction of a vaccine as a step that would be introduced along with the various reintroduction measures — not as a be-all and end-all.

“You would hope that a vaccine would be introduced in the process of forming these concentric circles,” he said.

The other method scientists hope will boost immunity to COVID-19 is taking blood plasma donations from people like Darren Campbell, who had the virus, recovered, and are expected to be immune.

Currently, there is a cross-country trial of convalescent plasma therapy, being led by Dr. Donald Arnold of McMaster University and co-ordinated by Canada’s two blood services. In the trial, people who have recovered from COVID-19 will be asked to donate blood plasma. Since it contains antibodies that fight the virus, it will be administered to COVID-19 patients, or to those who come into contact with the virus, in the hope that it will boost immunity.

Still, much is unknown about how effective antibodies will be at warding off the virus — and for how long.

Shih, who is co-ordinating the trial on the West Coast, said it will take months before the result will be known, but about 1,600 coronavirus patients in Canada will get access to the experimental treatment in the process, and doctors believe it to be very safe.

“Specifically, if you have a patient who is ill with COVID-19 but hasn’t had the most serious illness,” Shih said, “If we transfuse them convalescent plasma can we stop them from going to that (serious disease)?”

It’s a hopeful prospect for Campbell, who wishes for as much immunity as possible without anyone else having to endure the ordeal he went through. He’s encouraged, for example, by the fact that neither his wife or kids ever displayed COVID-19 symptoms, even though they were in proximity to him.

“If we can donate blood that could help some people — I haven’t yet heard a call for volunteers, but I’d be willing to do that as well,” Campbell said.

Having fully recovered, Campbell is just grateful to be with his family — all of them healthy — working from home, and waiting for the snow to stop in Ottawa so they can spend a bit more time outdoors.