Anticipating the Impact of Coronavirus in the Coming Fall

Across the United States, thousands of people with COVID-19 are being hospitalized each week and the number is steadily trending up — a sure sign that overall cases have also been on the rise.

Levels of detectable coronavirus in wastewater samples and the proportion of tests that come back positive have certainly been ticking up since June, data from the U.S. Centers for Disease Control and Prevention show. Both metrics indicate rising cases at the national level, albeit indirectly. It’s hard to get a good grasp of the start of new surges or know what’s happening within communities, in part because states are no longer required to report new cases, a result of the U.S. public health emergency ending in May (SN: 5/4/23).

We do know the worst of the pandemic is largely behind us. While the virus can, and does, still spread far and wide, its transmission isn’t the overwhelming crush that characterized the pandemic’s first years.

Amid a backdrop of ever-evolving variants — including a new version of omicron designated BA.2.86 that is under close watch from global and U.S. health agencies — most infections are now less deadly than the pandemic’s early days. Data from blood banks show that as of September 2022, around 96 percent of people in the United States had been vaccinated, infected with the virus or both, which can help reduce the severity of future infections. And, a new booster shot — designed to target relatives of a viral lineage dubbed XBB — should be available at the end of September (SN: 1/13/23).

Even with those rays of hope, our future with SARS-CoV-2, the virus that causes COVID, is unclear. The virus is not going anywhere; new variants will continue to appear with varying degrees of infectiousness and severity. How many people might fall ill or die on average each year? We don’t know.

Answering that question requires the virus to have entered its endemic phase — when it regularly circulates at some baseline amount. Even then, endemic does not mean benign. In that phase, people will still get sick with COVID, some severely so. But far fewer will land in the hospital or die in a “normal” year than during the pandemic years.

To see if this fall — our fourth with COVID and the first without a public health emergency in place — could possibly be the start of the coronavirus’ endemic phase, Science News spoke with epidemiologist Aubree Gordon of the University of Michigan in Ann Arbor. This conversation has been edited for length and clarity.

SN: How are things different this fall than in previous years?

Gordon: One of the big differences … is that at this point pretty much everybody … has some sort of immunity against SARS-CoV-2.

A majority of people have hybrid immunity, meaning that most people in the United States, or a good chunk of them, have been not only vaccinated but had an infection. For a majority of people that did not choose to get vaccinated, most of those individuals have been infected a few times. And some of the people who were vaccinated have been infected a few times.

What that means is that we have a higher level of immunity against the virus. Obviously, that’s not preventing people from getting infected or reinfected. But it’s certainly helping to reduce the severity of those infections when they happen.

SN: What have we learned about what reinfections tend to look like?

Gordon: They tend to be a lot milder than a first infection. But severe reinfections still do occur. And when you talk about severe, you’re not only thinking about fatal infections, which are of course the most severe, but also infections that cause hospitalization or may cause long-term symptoms.

SN: A new booster this fall will replace the omicron variant with a new one. Is it important to get this booster?

Gordon: I think booster shots are definitely advised, particularly for individuals who are more likely to have severe disease.

I had really hoped that we would have arrived at a point where SARS-CoV-2 was looking like a seasonal coronavirus, one that causes symptoms of the common cold, and was therefore less severe than influenza. What we’re still seeing for SARS-CoV-2 is that it is more severe than flu. It’s still causing a lot more deaths on an annual basis than flu is causing. I’d say it’s not clear if we’ve gotten to the fully endemic level yet [when transmission falls into an average range from year to year].

SN: Where do you think we are on the spectrum between pandemic and endemic?

Gordon: I think we’re getting pretty close to what endemic will look like. I don’t know if we’ll be fully at that level for this next season, or if it might take another season or two for us to get there.

I will say that I’m kind of hoping we’re not at the endemic level yet. At least based on last year, because there were a substantial number of deaths in the United States — 244,000 was the CDC estimate. It’s four or five times higher than a severe seasonal influenza season in the United States.

But [COVID disease severity] has been trending downward over the last many months. The hope would be that we continue to see that downward trend in the number of severe and fatal cases. If [COVID] had hit its endemic level, we would expect some season-to-season fluctuations, but it’d be fluctuating around that number rather than continuing a downward trend of being less and less severe. 

SN: Have researchers learned anything over the past year about what endemic might look like?

Gordon: I think we’re zeroing in on what endemic will look like. It’s, I think, become fairly clear that this is going to be a regular infection that people may get more often than flu. Maybe the virus will start changing less. For adults [who are more likely than kids to get severely ill], it is probably looking like it’s going to [be as dangerous as] influenza if not [more dangerous]. We will see for sure.

I had thought that everybody would need maybe a vaccination and then one or two infections to get at whatever the endemic level would be. It’s possible that you need a little bit broader immunity [to protect against more variants of the virus] and more exposures to hit that endemic level.

SN: What do you think experts might learn this fall?

Gordon: One thing that we’ll look at this fall is how different it is from last fall. Because if we’re still seeing a downward trajectory, then maybe we haven’t yet hit the endemic level. Or we may see something that looks quite similar to last fall, which would tell us that perhaps we’ve arrived at that endemic level.

There is season-to-season variability, there are differences in variants, and we have new variants arising, which will all contribute on a yearly basis to how severe the SARS-CoV-2 season is. We have that for flu. CDC estimates for recent flu seasons, excluding the pandemic ones, were anywhere from 12,000 to 52,000 deaths a year. That’s quite a bit of variability.