Is The Worst Over? Models Predict A Steady Decline In COVID Cases Through March

Sep 22, 2021
Originally published on September 23, 2021 8:30 am

Americans may be able to breathe a tentative sigh of relief soon, according to researchers studying the trajectory of the pandemic.

The delta surge appears to be peaking nationally, and cases and deaths will likely decline steadily now through the spring without a significant winter surge, according to a new analysis shared with NPR by a consortium of researchers advising the Centers for Disease Control and Prevention.

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For its latest update, which it released Wednesday, the COVID-19 Scenario Modeling Hub combined nine different mathematical models from different research groups to get an outlook for the pandemic for the next six months.

"Any of us who have been following this closely, given what happened with delta, are going to be really cautious about too much optimism," says Justin Lessler at the University of North Carolina, who helps run the hub. "But I do think that the trajectory is towards improvement for most of the country," he says.

The modelers developed four potential scenarios, taking into account whether or not childhood vaccinations take off and whether a more infectious new variant should emerge.

The most likely scenario, says Lessler, is that children do get vaccinated and no super-spreading variant emerges. In that case, the combo model forecasts that new infections would slowly, but fairly continuously, drop from about 140,000 today now to about 9,000 a day by March.

Deaths from COVID-19 would fall from about 1,500 a day now to fewer than 100 a day by March 2022.

That's around the level U.S. cases and deaths were in late March 2020 when the pandemic just started to flare up in the U.S. and better than things looked early this summer when many thought the pandemic was waning.

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And this scenario projects that there will be no winter surge, though Lessler cautions that there is uncertainty in the models and a "moderate" surge is still theoretically possible.

There's wide range of uncertainty in the models, he notes, and it's plausible, though very unlikely, that cases could continue to rise to as many as 232,000 per day before starting to decline.

"We have to be cautious because the virus has shown us time and time again that new variants or people loosening up on how careful they're being can lead things to come roaring back," Lessler warns.

William Hanage, an epidemiologist at Harvard's T.H. Chan School of Public Health, notes there is a fair amount of uncertainty in the models. "I would be concerned about interpreting these in an overly optimistic fashion for the country as a whole," he says.

He agrees that overall the pandemic will be "comparatively under control by March," but says "there could be a number of bumps in the road."

Last winter, the worst surge of the pandemic in the U.S. hit midwinter when weather was cold and more people spent time indoors. "If you look at the seasonal dynamics of coronaviruses, they usually peak in early January. And in fact, last year we saw a peak like that with SARS-CoV-2," he says.

Both Hanage and Lessler note that there will be regional variation with some states continuing to surge for possibly a few weeks. Essentially, things could still get worse in some places before they get better.

Lessler says he is especially worried about Pennsylvania, for example, and he notes that in some Western states like Idaho and Utah, there's a risk of resurgence. Hanage notes that places with cold winter weather may be susceptible to some increase in cases later in the year.

And hospitals are going to continue to get flooded with patients for a while before infections taper off, and many are already being pushed past the breaking point.

Another caveat: This scenario assumes that the U.S. doesn't get hit with a new variant that's even more contagious than delta. If it does, a bleaker scenario from the Modeling Hub projects far worse numbers: just below 50,000 cases a day by next March. But Lessler emphasizes this is very hypothetical.

He's hopeful that the most optimistic scenario is the most likely.

"I think a lot of people have been tending to think that with this surge, it just is never going to get better. And so maybe I just need to stop worrying about it and take risks. But I think these projections show us there is a light at the end of the tunnel," he says.

Lessler thinks that at this point there's enough immunity in this country from a combination of enough people getting vaccinated and enough people having been exposed to the virus.

"The biggest driver is immunity," he explains. "We've seen really big delta waves. The virus has eaten up the susceptible people. So there are less people out there to infect." The virus is still fighting back, he says, but "immunity always wins out eventually."

But transmission is still very high and will remain so for a while, so precautions are still called for until new infections come down to moderate levels.

Natalie Dean, an assistant professor of biostatistics at Emory University, notes that even though we may see a decline this fall, we will still see "a lot of cases and deaths."

Getting everyone who is eligible vaccinated is still key to preventing further deaths. Even in this optimistic scenario, the U.S. is projected to reach a cumulative total of more than 780,000 deaths by March.

Modeling is an imprecise science, but the Modeling Hub brings together many of the the top disease modelers around the country, doing their best to look far down the road and make sense of a very unpredictable, complicated pandemic that's thrown one curve ball after another.

"I hope it's true, obviously, but I can't shake a little unease I have about what could be coming," says Dean.

So like many Americans, Dean is keeping her fingers crossed.

Copyright 2021 NPR. To see more, visit https://www.npr.org.

RACHEL MARTIN, HOST:

We have just moved into autumn, but it's hard not to wonder what this winter in the pandemic will look like. According to a new analysis made available to NPR by a group of researchers advising the CDC, this winter season may not be as bad as a lot of us had feared. NPR health correspondent Rob Stein joins us now. Hi, Rob.

ROB STEIN, BYLINE: Good morning, Rachel.

MARTIN: I mean, this sounds pretty good.

STEIN: Yeah.

MARTIN: Where exactly is this analysis coming from?

STEIN: So, you know, this comes from the COVID-19 Scenario Modeling Hub. It combines nine different mathematical models that project the possible scenarios over the next six months and, for the first time, factors in the impact of vaccinating children ages 5 to 11, which could start as soon as November. I talked about the findings with Justin Lessler at the University of North Carolina. He helps run the hub. He's cautiously optimistic that the worst may really finally be behind us now.

JUSTIN LESSLER: Any of us who've been following this closely, given what happened with delta, are going to be really cautious about too much optimism. But I do think that the trajectory is towards improvement for most the country now, and I'm fairly confident that it'll continue to move that way.

STEIN: In fact, the most likely scenario says that the number of people catching the virus every day would slowly but fairly continuously drop from about 140,000 today to about 9,000 a day by mid-March, and the number of people dying from COVID-19 would fall from about 1,500 a day now to far fewer than 100 a day by March, so better than where we were when everyone thought the pandemic was finally starting to be behind us early this summer.

MARTIN: As much as I'd like to just lean totally 100% into this optimism...

STEIN: Yeah, I know.

MARTIN: ...You know, it's true, though, that the pandemic has affected different parts of the country in different ways, right?

STEIN: Yeah, yeah.

MARTIN: So, you know, are we going to see all this improvement in some places and not in others?

STEIN: Yeah, yeah, Rachel. You're totally right. According to the most likely scenario, the U.S. wouldn't go through another horrible winter surge like last year, but there are several important caveats. This is what the overall national trend would be. The modeling indicates that a lot of variation around the country could occur, with some states continuing to surge for possibly weeks. So things could still get worse in a lot of places before getting better. Lessler is especially worried about, like, Pennsylvania, for example. And hospitals are far from out of the woods yet. And this assumes, for example, that another possibly even more contagious variant doesn't explode.

MARTIN: Right.

STEIN: But, you know, given all that, Lessler is still optimistic that the most optimistic scenario is the most likely.

LESSLER: I think a lot of people have been tending to think that with this surge that, OK, this just means it's never going to get better, and so maybe I just need to stop worrying about it and take the risk. But I think these projections show us and the data shows us that things are going to be getting better, that there is a light at the end of the tunnel.

MARTIN: All right. So let's talk about how - how he thinks this.

STEIN: Yeah.

MARTIN: Why does he think this? Why wouldn't another bad surge happen?

STEIN: Yes, that's a very good question. You know, you'd think it would surge again, given what happened last winter and given the fact that respiratory viruses tend to spread more easily when the weather gets colder and people spend more time indoors; you know, kids are back in school. But Lessler thinks that, at this point, there's enough immunity in this country from a combination of enough people getting vaccinated and enough people just having been exposed to the virus at this point.

LESSLER: The biggest driver is immunity. We've seen a lot of delta. We've seen really big delta waves. You know, the virus has eaten up the susceptible people. So there are just - are less people out there to infect. That's, of course, also driven by additional people getting vaccinated and other behavior change, from mask-wearing to other precautions. But I think the biggest driver is that accumulation of immunity.

STEIN: But, you know, people have to keep getting vaccinated and taking those precautions to keep the pandemic in check as even more people develop immunity.

MARTIN: Yeah. So do other researchers agree with these findings?

STEIN: You know, this is a very well-respected group that brings together many of the top disease modelers around the country. But everyone's pretty gun-shy about looking this far down the road, especially given how complicated this pandemic has been and how many curveballs the virus has already thrown at us. Here's Natalie Dean from Emory.

NATALIE DEAN: I hope it's true, but I can't shake a little unease I have about what could be coming.

STEIN: You know, so like the rest of us, Dean is just keeping her fingers crossed.

MARTIN: Right. And just - in seconds remaining, Rob, what's the latest on boosters?

STEIN: Yeah. So a key CDC advisory group is starting a two-day meeting today about the Pfizer booster to see if they go along with the FDA's recommendation - that's expected any time - that a Pfizer booster be given to anyone over age 65 and older, anyone at high risk who got the Pfizer booster six months ago. So it's a possibility boosters could start rolling out later this week if things go according to plan.

MARTIN: OK. NPR health correspondent Rob Stein. Thank you.

STEIN: You bet, Rachel. Transcript provided by NPR, Copyright NPR.