HEALTH

Our Most Reliable Pandemic Number Is Losing Meaning

A new study suggests that almost half of those hospitalized with COVID-19 have mild or asymptomatic cases.
By David Zweig

...The authors of the paper out this week took a different tack to answer a similar question, this time for adults. Instead of meticulously looking at why a few hundred patients were admitted to a pair of hospitals, they analyzed the electronic records for nearly 50,000 COVID hospital admissions at the more than 100 VA hospitals across the country. Then they checked to see whether each patient required supplemental oxygen or had a blood oxygen level below 94 percent. (The latter criterion is based on the National Institutes of Health definition of “severe COVID.”) If either of these conditions was met, the authors classified that patient as having moderate to severe disease; otherwise, the case was considered mild or asymptomatic.

The study found that from March 2020 through early January 2021—before vaccination was widespread, and before the Delta variant had arrived—the proportion of patients with mild or asymptomatic disease was 36 percent. From mid-January through the end of June 2021, however, that number rose to 48 percent. In other words, the study suggests that roughly half of all the hospitalized patients showing up on COVID-data dashboards in 2021 may have been admitted for another reason entirely, or had only a mild presentation of disease.

This increase was even bigger for vaccinated hospital patients, of whom 57 percent had mild or asymptomatic disease. But unvaccinated patients have also been showing up with less severe symptoms, on average, than earlier in the pandemic: The study found that 45 percent of their cases were mild or asymptomatic since January 21. According to Shira Doron, an infectious-disease physician and hospital epidemiologist at Tufts Medical Center, in Boston, and one of the study’s co-authors, the latter finding may be explained by the fact that unvaccinated patients in the vaccine era tend to be a younger cohort who are less vulnerable to COVID and may be more likely to have been infected in the past.

...One of the important implications of the study, these experts say, is that the introduction of vaccines strongly correlates with a greater share of COVID hospital patients having mild or asymptomatic disease. “It’s underreported how well the vaccine makes your life better, how much less sick you are likely to be, and less sick even if hospitalized,” Snyder said. “That’s the gem in this study.”

“People ask me, ‘Why am I getting vaccinated if I just end up in the hospital anyway?’” Griffin said. “But I say, ‘You’ll end up leaving the hospital.’” He explained that some COVID patients are in for “soft” hospitalizations, where they need only minimal treatment and leave relatively quickly; others may be on the antiviral drug remdesivir for five days, or with a tube down their throat. One of the values of this study, he said, is that it helps the public understand this distinction—and the fact that not all COVID hospitalizations are the same.

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