Some experts speculate that the pandemic coronavirus will one day cause nothing more than a common cold, mostly in children, where it will be an indistinguishable drip in the steady stream of snotty kid germs. Such is the reality for four other coronaviruses that have long stalked school yards and commonly circulate among us every cold and flu season, to little noticeable effect.

But that sanguine—if not slightly slimier—future is shaky. And the road to get there will almost certainly be rocky. For the pandemic coronavirus to turn from terror to trifle, we have to build up high levels of immunity against it. At the population level, this will be difficult—even with vaccines. And with the uncertainty of how we’ll pull it off, some experts are cautioning that we should prepare for the possibility that the pandemic coronavirus, SARS-CoV-2, will stick with us for the near future, possibly becoming a seasonal surge during the winter months when we’re largely indoors.

“The prospect of persistent and seasonal COVID-19 is real,” write public health expert Christopher Murray of the University of Washington and infectious disease expert Peter Piot of the London School of Hygiene and Tropical Medicine. In a recent commentary in the Journal of the American Medical Association, the two warn that if that happens, it “could require both health system change and profound cultural adjustment for the life of high-risk individuals in the winter months. There is an urgent need to prepare for such a scenario.”

Before getting to steps we can take to prepare, Murray and Piot lay out how SARS-CoV-2 may morph into a seasonal scourge, starting with tempering optimism over vaccines.

Wobbly immunity

With the pandemic just over one year old, several vaccines have already proven highly effective against COVID-19 and are rolling out worldwide—a true marvel of modern medicine. The Biden administration recently set the ambitious target of having enough vaccine doses for every American adult by the end of May. But there’s a reasonable chance that we will close out 2021 without reaching high levels of vaccination and immunity in the population.

For one thing, a considerable chunk of American adults will likely decline vaccination. The latest poll from the Pew Research Center suggests that 30 percent of adults may eschew a shot. Though that number has shrunk in recent months, there’s still 15 percent who say they would “definitely” not get vaccinated.

And that’s just speaking of the roughly 75 percent of the population that is currently eligible for vaccination: adults. While kids make up about a quarter of the US population, there is yet to be a vaccine authorized for people under the age of 16.

Moreover, even in people who are eligible and accepting of the shots, the vaccines are not 100 percent effective. The two mRNA vaccines authorized for use in the US—the Moderna and Pfizer/BioNTech vaccines—are around 95 percent effective at preventing symptomatic COVID-19, which is very impressive and certainly very close to, but not quite, 100 percent. The Johnson & Johnson vaccine was found to be 72 percent effective against symptomatic COVID-19 in the US, which is also a very strong efficacy rate for a vaccine, but not 100 percent.

But do note, these numbers are just for symptomatic infections. It’s still unclear how well the vaccines protect against infection and asymptomatic disease. Some early data suggests that the vaccines do protect against asymptomatic COVID-19 but at lower rates than the protection against symptomatic illness. Thus, vaccinated people may still catch—and spread—SARS-CoV-2.

Durability

Last, we don’t know exactly how long protection from SARS-CoV-2 will last, regardless of whether that protection is from natural infections or vaccines. Some immune memory is likely to stick around for years and help protect us from severe disease and death. But for people whose protection is strong enough to prevent reinfection, that protection may be shorter lived. Whether that protection—called sterilizing immunity—may last on the order of months, years, or decades, is yet to be seen.

Studies suggest that sterilizing immunity from garden-variety coronaviruses only lasts on the order of months for most people, leaving them open to reinfection after a year or so. That’s how those school-yard coronaviruses—dubbed 229E, NL63, OC43, and HKU1—come around every cold and flu season. After decades of circulating, they mostly hit young children, who haven’t yet built up immunity from previous seasons. In adults who have those years of immunity, the coronaviruses generally cause only trifling cold symptoms.

As mentioned before, some experts think SARS-CoV-2 will reach this same fate—eventually. We have to build up immunity in adults first. But it’s possible that people infected with SARS-CoV-2 at the beginning of the pandemic may become vulnerable to reinfection in the near future, before they can have their immune responses boosted by a vaccine. And that may mean more surges of disease before we get to those schoolyard sniffles.

Straying from the herd

With all the factors taken together—vaccine uptake, efficacy, and indefinite durability of immune responses—there’s a good chance that SARS-CoV-2 will continue circulating, reaching people who are still vulnerable or have waning immunity. This may mean a rocky few years ahead. It also certainly suggests that we’re unlikely to reach the much-discussed point of herd immunity—that is, when the percentage of people with protective immunity (either from vaccination or infection) reaches a high enough point that the virus simply cannot spread. It’s still unclear how high that percentage has to be to achieve herd immunity, but experts often put it in the realm of 70 percent. And if that’s the case, our chances of reaching it are low.

If this picture wasn’t already anxiety-inducing, the immune-evading variants emerging in various countries threaten to further erode vaccine efficacy and population-level immunity. In their commentary, Murray and Piot note that the variant B.1.351, first identified in South Africa, already seems to reinfect people who have recovered from COVID-19 and knock back the efficacy of some vaccines. For instance, while the Johnson & Johnson vaccine had a 72 percent efficacy in the US, where there were no known concerning variants circulating, the vaccine’s efficacy fell to 64 percent in South Africa while B.1.351 was circulating at high levels.

The good news is that even with the reduced efficacy against symptomatic disease, the Johnson & Johnson vaccine was still around 85 percent effective against severe disease, even in South Africa. Still, looming variants paint a grim picture for population immunity overall, particularly if they become the predominant viruses circulating.

Rough estimates

Murray and Piot put some back-of-the-envelope numbers to this scenario, trying to account for the drop in efficacy against symptomatic disease from a variant. They come to the rough estimate that “[i]f the B.1.351 variant becomes dominant, a simple calculation suggests that the aggregate effectiveness of vaccines for preventing B.1.351 transmission in the US could be only 50 percent.” The estimate drops to 37.5 percent when they fold in the estimate of people who will refuse vaccination.

All this means that there’s a real possibility that we could see surges in COVID-19 for the near future, especially if variant-specific vaccines are eventually needed. Piot and Murray suggest these surges could be seasonal, corresponding to when we normally see surges in common coronaviruses. This also aligns with winter months, when we spend more time indoors in less ventilated spaces together, which all help SARS-CoV-2 spread.

The two experts lay out five strategies to prepare for this unpleasant possibility: 1) Help intensify global vaccination to squash the emergence of variants; 2) Step up monitoring for variants; 3) Ready hospitals for winter surges; 4) Work to reduce transmission in the off-season; and 5) Prepare high-risk individuals for winter mitigation efforts, such as seasonal physical distancing.

It’s too early to know for sure if seasonal COVID-19 lies ahead. There’s still a lot of uncertainty, Murray and Piot note. But it’s a real possibility, and we should prepare now. “If new variants continue to appear, winter surges may become the norm,” they write. “This prospect requires advance planning and consideration of a range of strategies to mitigate the consequences for communities and health systems.”

https://arstechnica.com/?p=1748537