Fall COVID surge begins in Europe—and US outlook already looks rough

The dreaded winter COVID wave may already be upon us—and based on early signs, we may be in for a rough time.

As people head indoors amid cooling weather, several European countries are seeing upticks in COVID-19 cases, hospitalizations, and deaths. Though the situation in the US remains quiet for now, trends in the US tend to echo those in Europe.

So far, the rise in cases is driven by a familiar foe: the omicron subvariant BA.5, which has maintained a relatively long reign as the globally dominant variant. But a thick soup of omicron subvariants is simmering on the back burner, loaded with sublineages—notably from BA.2. and BA.5—converging on alarming sets of mutations. Some sublineages—such as BQ.1.1, an offshoot from BA.5, and XBB, derived from BA.2 strains—are the most immune evasive subvariants seen to date.

For now, the sublineages only account for a sliver of total cases we know about, with BA.5 still taking the lion's share. But our ability to detect and surveil new subvariants is only a fraction of what it once was.

Low surveillance

"Surveillance has changed drastically in the last several months," Maria Van Kerkhove, COVID-19 technical lead for the World Health Organization, said in a press briefing Wednesday. "The number of sequences that the world and our expert networks are evaluating has dropped by more than 90 percent since the start of the year. That limits our ability to really track each of these [omicron subvariants]."

Still, even what we can see from that limited surveillance is concerning. Van Kerkhove notes that there are more than 300 sublineages that experts are tracking, and several are particularly worrying. "It sounds a little bit like an alphabet soup with all of these subvariants that we're tracking," she said. "But the bottom line is that this virus continues to evolve. It's circulating at an incredibly intense level around the world right now. …  We will continue to see waves of infection. This is for sure."

Many experts expect the next wave to be coming in the weeks ahead—and the best way to protect from a surge in hospitalizations and death is for people to get boosted. But yet another concerning reality is that booster uptake in the US has been and is abysmal. While 68 percent of the US population has received a full primary series of COVID-19 vaccines, less than half have gotten a single booster. Only 37 percent of people over the age of 50 have gotten a second booster. And, to date, only 7.6 million Americans have gotten their fall booster—a dose of the new, bivalent booster that, in part, targets BA.5.

Weak boosting

A modeling study released Wednesday by researchers at Yale Univesity and the Commonwealth Fund highlights how concerning this poor booster rate is. The researchers modeled a winter wave—assuming no new subvariant, like XBB, sweeps the globe like omicron did last winter. They compared the outlook with current vaccination and booster rates to what could be averted if those rates mirrored the coverage of influenza vaccine in the 2020-2021 flu season—which was modest but solid 59 percent for those aged 6 months to 17 years, and 50 percent among adults.

In a conservative estimate, "if vaccination continued at its current pace through the end of March 2023, a potential winter surge in COVID-19 infections could result in a peak of around 16,000 hospitalizations and 1,200 deaths per day by March 2023," the researchers found. But, if the fall COVID-19 booster campaign matched the modest vaccination levels of the 2020-2021 flu season, it would prevent more than 75,000 deaths and more than 745,000 hospitalizations by March 2023.

And these are conservative estimates in that they assume the new boosters aren't better than the previous versions, there is no holiday-related surge, and loosened quarantine and isolation guidance don't exacerbate spread. Thus, the modeled wave is likely an underestimate of what could happen.