A Blog by Jonathan Low


Dec 29, 2021

How Covid Is Evolving From Pandemic To Endemic

There is some evidence it is already happening, despite - or perhaps because of - the rise in omicron cases. JL 

Sigal Samuel reports in Re/code:

We’re not going to totally eradicate Covid-19, but it will move out of the pandemic phase into the endemic phase. Endemicity means the virus will keep circulating in parts of the global population for years, but its impact will come down to manageable levels, so it ends up more like flu than a world-stopping disease. For an infectious disease to be classed in the endemic phase, the rate of infections has to stabilize across years, rather than showing big, unexpected spikes. We’ll know endemicity has arrived when vaccines, rapid tests, antibody pills and ventilation enable us to adapt to the virus, as the virus has adapted to us.

With omicron rates soaring, you may find yourself despairingly asking when — or even if — this pandemic is ever going to end.

The good news is that it will end. Experts agree on that. We’re not going to totally eradicate Covid-19, but we will see it move out of the pandemic phase and into the endemic phase.

Endemicity means the virus will keep circulating in parts of the global population for years, but its prevalence and impact will come down to relatively manageable levels, so it ends up more like the flu than a world-stopping disease.

For an infectious disease to be classed in the endemic phase, the rate of infections has to more or less stabilize across years, rather than showing big, unexpected spikes as Covid-19 has been doing. “A disease is endemic if the reproductive number is stably at one,” Boston University epidemiologist Eleanor Murray explained. “That means one infected person, on average, infects one other person.”

We’re nowhere near that right now. The highly contagious omicron variant means each infected person is infecting more than one other person, with the result that cases are exploding across the globe. Nobody can look at the following chart and reasonably conclude that we’re in endemic territory.

Our World in Data

Looking at this data might make you wonder about some of the predictions that were floating around before omicron came on the scene. In the fall, some health experts were saying that they thought the delta variant might represent the last big act for this pandemic, and that we could reach endemicity in 2022.

The outlook is more uncertain now. So how should you be thinking about the trajectory and timeline of the pandemic going into the new year? And how should omicron be shaping your everyday decision-making and risk calculus?

When we’ll know we’re finally in “endemic” territory

Here’s one big question you’d probably like the answer to: Does omicron push endemicity farther off into the future? Or could it actually speed up our path to endemicity by infecting so much of the population so swiftly that we more quickly develop a layer of natural immunity?

“That is really the million-dollar question,” Angela Rasmussen, a virologist at the University of Saskatchewan in Canada, told me. “It’s really hard to say right now.”

That’s partly because endemicity isn’t just about getting the virus’s reproductive number down to one. That’s the bare minimum for earning the endemic classification, but there are other factors that come into play, too: What’s the rate of hospitalizations and deaths? Is the health care system overburdened to the point that there’s a precipitous space or staffing shortage? Are there treatments available to reduce how many people are getting seriously ill?

In general, a virus becomes endemic when we (health experts, governmental bodies, and the public) collectively decide that we’re okay with accepting the level of impact the virus has — that in other words, it no longer constitutes an active crisis.

With omicron surging right now and many governments reimposing stricter precautions as a result, it’s clear we’re still in crisis mode. “But so much depends on the burden it’ll place on the healthcare system,” Rasmussen said. “And that’s going to be different from community to community.”

Even if it turns out to be true that omicron tends to result in milder disease than previous variants (we don’t yet have enough data to say conclusively), a massive increase in cases could still lead to a big increase in hospitalizations and deaths. That could further stress health care systems that are already in dire straits. That’s why Rasmussen concludes that “omicron certainly has the potential to delay endemicity.”

But there are also some hopeful things to bear in mind. “The incredible number of infections is building up population-level immunity. That’ll be crucial in terms of muting future waves,” said Joshua Michaud, associate director for global health policy at the Kaiser Family Foundation.

In addition to omicron potentially building up some immunity in the vast numbers of people who are becoming infected with it, vaccinations and boosters are also contributing to “a significant immunity wall that’s being built,” he said. But he cautioned that “that’s a wall to the variants we’ve seen already. There could be another variant which could evade immunity down the road.” Some experts are already conjecturing that getting infected with omicron may not give you much cross-protection against other variants, though a small early study showed positive signs on that front.

This is why Ramussen says “the key determinant” of when the pandemic ends is how long it will take to make vaccines accessible around the world (and to combat ongoing vaccine hesitancy). Currently, we’re not vaccinating the globe fast enough to starve the virus of opportunities to mutate into something new and serious. “If only a very small proportion of people are getting access to vaccines, we’re just going to keep playing variant whack-a-mole indefinitely,” Rasmussen said.

In the meantime, we do have another ace up our sleeves, which will hopefully also become available around the globe sooner rather than later: new treatments  like Pfizer’s paxlovid, recently approved by the Food and Drug Administration, and Merck’s molnupiravir, also FDA approved — that reduce the rates of hospitalization and death from Covid-19.

“Very important in the context of endemicity is the antiviral pills,” Michaud said. “If we have those tools, we’re looking at a very different state going into 2022. People shouldn’t feel like we’re back to square one.”

We’re not back to March 2020. But it makes sense to modify our behavior during the omicron surge.

Dire headlines notwithstanding, we’re in much better shape than we were at the start of the pandemic. We’ve discovered a lot more information about how Covid-19 works. We’ve manufactured effective masks, vaccines, boosters, treatments, and rapid tests.

We’ve also learned that having to hunker down comes at a real cost to our mental and economic health and wellbeing. The cost of a strict lockdown may have been worthwhile in March 2020, but by and large, that’s not what US experts are advising now.

They are, however, urging us to take more precautions than we might have been in the weeks leading up to omicron.

Take Bob Wachter, for example, the chair of the department of medicine at the University of California San Francisco. In the fall, he shifted from being very cautious about Covid-19 to taking some more calculated risks, including dining indoors at restaurants and even hosting an in-person medical conference with 300 attendees. But now that omicron is causing cases to skyrocket, he’s being more cautious again.

“I see the next few months as a time to fortify one’s safety behaviors,” he wrote on Twitter. Here’s how he explained his reasons:

The other experts I spoke to agreed that now is a time to limit risky activities.

“I had taken my foot off the brakes in terms of my own behavior. But I’ve now started to put it on again,” Michaud told me. “I canceled plans to go to New Jersey to visit my family over Christmas. I’m avoiding more indoor environments. As of now, it does make a lot of sense to me to take additional steps to prevent yourself and those around you from getting infected.”

After the omicron wave passes, he said, he envisions relaxing precautions again. Modeling suggests that omicron could peak in mid- to late January in the US, with case rates steeply declining — and activities becoming correspondingly safer again — in February.

Rasmussen is also modifying her behavior in light of omicron, though she emphasizes that’s not the same as going back to a spring 2020-style lockdown. Although she canceled an international flight over the holidays, she still felt comfortable going over to her colleague’s house for a Christmas meal. That’s because she and they had vaccinations, boosters, rapid tests, and great ventilation working in their favor.

“We have a lot more tools at our disposal for dealing with this than we did in March 2020,” she said.

We’ll know endemicity has arrived when those tools — and the long, painful experience of the pandemic itself — has enabled us to fully adapt to the virus, as the virus has adapted to us.


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