This is interesting; an excerpt:
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.
Among the limitations of the study is that patients in the VA system are not representative of the U.S. population as a whole, as they include few women and no children. (Still, the new findings echo those from the two pediatric-admissions studies.) Also, like many medical centers, the VA has a policy to test every inpatient for COVID, but this is not a universal practice. Lastly, most of the data—even from the patients admitted in 2021—derive from the phase of the pandemic before Delta became widespread, and it’s possible that the ratios have changed in recent months. The study did run through June 30, however, when the Delta wave was about to break, and it did not find that the proportion of patients with moderate to severe respiratory distress was trending upward at the end of the observation period.
