'COVID-19 Hospitalizations' Are an Increasingly Misleading Measure of Severe Disease

Since the beginning of the COVID-19 pandemic, researchers, policy makers, and journalists have viewed hospitalizations as an important indicator of the disease burden, often citing increases in that measure as a justification for government interventions aimed at curtailing virus transmission, such as business restrictions and mask requirements. Hospitalization numbers do have advantages over case tallies, which are highly dependent on who happens to be tested, and fatality reports, which are a lagging indicator, since deaths may be recorded weeks after diagnosis. But because hospitalization rates reflect patients who test positive for COVID-19, they do not tell us how many were admitted for treatment of the disease or how many experienced severe symptoms.

A newly published preprint study addresses those gaps in knowledge by applying measures of disease severity to about 48,000 V.A. hospital admissions of more than 38,000 COVID-positive patients between March 1, 2020, and June 30, 2021. The researchers, all but one of whom work for the V.A. Boston Healthcare System, found that the share of admissions involving moderate-to-severe COVID-19 cases fell from 64 percent before vaccines were widely available to 52 percent afterward.

In other words, incidental or mild cases accounted for a rising share of so-called COVID-19 hospitalizations—nearly half by the end of June. That means it is increasingly problematic to treat that number, which includes COVID-19 patients without life-threatening symptoms as well as COVID-positive patients admitted for other reasons, as an indicator of severe disease. Notably, the Centers for Disease Control and Prevention (CDC), which collects data on what are commonly called "COVID-19 hospitalizations," uses a more ambiguous term: "COVID-19-associated hospitalizations." But even that description is misleading, since the tally includes many hospital patients who were not admitted for treatment of COVID-19.