COVID-19: When the pandemic becomes endemic, it may or may not be a less-dangerous disease

It's unclear whether an annual COVID booster shot will be needed, or any vaccine at all

Nathan Griffiths 4 minute read January 24, 2022

Health officials have starting talking about COVID-19 ceasing to be a pandemic and becoming endemic.

“This is a real transition in moving out of a pandemic and learning to live with this virus,” Dr. Bonnie Henry said recently. “If we make it to Easter, I think we’re going to be in a really different place.”

A shift from pandemic to endemic doesn’t necessarily mean COVID will be less dangerous, however.

Q: What’s the difference between pandemic and endemic?

A pandemic involves the uncontrolled spread of an infection, such as COVID, something countries across the globe have experienced over the past 18 months.

An endemic disease is one that is consistently present, sometimes limited to a particular region or a particular time of year. This makes the disease’s spread and rates much more predictable. Malaria in tropical countries is perhaps the best-known example of an endemic disease.

“What endemic doesn’t mean to me is really, really low,” cautioned Caroline Colijn, professor and Canada 150 research chair in mathematics, “or when you get it, it’s not severe.”

Some other endemic diseases include HIV, hepatitis C and many of the common flus that appear each year. Many seasonal flus are believed to be mutations of the deadly Spanish flu of 1918 that killed an estimated 50 million people around the world.

An epidemic disease is one that spreads quickly and affects many people in a limited geographic area. Both the West Nile virus and the rapid increase in obesity rates in the developed world are considered epidemics, for example.

Q: When will COVID be endemic?

A 2021 survey of immunologists, infectious disease researchers and virologists by the science journal Nature found that 89 per cent believe COVID is likely to become endemic. When exactly it will switch from being a pandemic to an endemic virus is unclear, however.

“I think we are heading into a period after this wave subsides where we really have low levels and we will be talking about it being endemic,” said Colijn.

She said there are four key things to consider in determining endemic status: transmissions rates, the length of immunity provided by getting vaccinated or getting sick, vaccine efficacy and COVID rates in neighbouring jurisdictions.

“Some of the dynamics can mean it wobbles up and down for years before it eventually settles into endemic,” Colijn said of COVID.

Q: Are endemic diseases less dangerous?

The difference between endemic, pandemic and epidemic diseases is more to do with their distribution than their danger.

“Endemic doesn’t necessarily mean you don’t have to worry about it,” said Colijn, who noted that tuberculosis, one of the world’s leading causes of infectious death, “is endemic in many places” around the world.

“We’ve heard officially from the World Health Organization that we should not consider (Omicron) a mild infection,” said Colijn.

Q: Will COVID ever disappear?

It’s rare for a disease to completely disappear. Two diseases that the WHO said have been eradicated are smallpox and rinderpest (a disease of cattle). Vaccinations were critical in ending both.

“I think we will have COVID with us,” said Colijn of the future. “After this wave, there’s no guarantee that it’s endemic and we’re done.

“On the plus side, we are building up a lot of immunity,” she said, adding that she thinks a regular COVID vaccine booster is likely “on the table” as part of the tool kit to fight the disease. Typically, for example, many people have some immunity to certain strains of the flu, because of earlier exposure to closely related strains.

The CEO of Pfizer said over the weekend that an annual vaccine, tailored for the latest variants of COVID-19, would be the best approach, if possible, as people are more likely to accept that than a jab every six months. Pfizer is retooling its mRNA vaccine for COVID to better protect against Omicron.

“The virus continues to evolve and immunity will continue to change and people’s immunity will wane,” Colijn said. “And when immunity wanes, you can get another wave.”

Q: What does that mean for the future?

A recently published study found that even when endemic, long-term levels of COVID wouldn’t necessarily be lower than current pandemic levels, depending on overall vaccination levels, transmissibility of variants, emergence of new variants, and other factors.

“I do hope that we will end up with another coronavirus that causes mostly mild illness,” said Henry, who noted that regular boosters may only be needed for older people or those with immune-compromised conditions.

“It may be that most of us who’ve now had the three doses won’t need to have periodic boosters,” she said.

It will take time and more research to see if that is, indeed, the case.

— With files from Gordon Hoekstra

ngriffiths@postmedia.com

twitter.com/njgriffiths


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