http://reason.com/2021/09/15/covid-19-hospitalizations-are-an-increasingly-misleading-measure-of-severe-disease/
New research shows incidental and mild infections account for a large
and rising share of that widely cited number.
JACOB SULLUM | 9.15.2021 1:55 PM
COVID-19-patient-Florida-8-25-21-Newscom
(John Pendygraft/Zuma Press/Newscom)
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,
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.
The main measure of disease severity in the V.A. study was an oxygen
saturation level below 94 percent, which corresponds with "the most
stringent cut-off" on a scale developed by the National Institutes of
Health. The researchers also considered whether patients received the
steroid dexamethasone, which reduces mortality in COVID-19 patients on
supplemental oxygen or mechanical respiratory support. By both measures,
the prevalence of moderate-to-severe cases declined with the advent of
vaccines.
The researchers cite two explanations for that trend: Vaccination
protects people against severe disease even if they are infected by the
coronavirus, and "unvaccinated patients tend to be younger and
healthier," meaning they are less likely to experience life-threatening
systems. Another factor could be the criteria that hospitals use for
admitting COVID-19 patients, which are apt to be less demanding when the
infected population becomes younger and healthier. But the upshot is
that "COVID-19-associated hospitalizations," which were always an
imprecise measure of severe disease, should be viewed with even more
caution now.
"Routine inpatient screening, common or mandated in many facilities, may
identify incidental cases," the researchers note. "If hospitalizations
are used as a metric for policy decision-making, patients hospitalized
for the management of COVID-19 disease should be distinguished from
patients who are hospitalized and incidentally found to be infected with
SARS-CoV-2." They argue that oxygen saturation levels and use of
supplemental oxygen, both of which are recorded by hospitals, are handy
ways to distinguish between these two groups. They suggest that
"reporting definitions may need to be revised to reflect the changing
nature of the pandemic, particularly in regions with high levels of
vaccine uptake."
The researchers note that "the VA population is not representative of
the US population as a whole, having few women and no children." But the
finding that mild cases account for a substantial share of hospitalized
COVID-positive patients is consistent with earlier research involving
pediatric populations.
A study reported in Hospital Pediatrics last month looked at 117
admissions to a children's hospital in Northern California between May
10, 2020, and February 10, 2021. Two-fifths of those "COVID-19
hospitalizations" involved patients who were asymptomatic. One-fifth
involved "severe" or "critical" cases.
Another study reported in the same journal last month looked at
COVID-positive patients younger than 22 who were treated by Valley
Children's Healthcare in Madera, California, between May 1, 2020, and
September 30, 2020. The researchers found that 40 percent of the
patients had "incidental infection," 47 percent were "potentially
symptomatic," and the rest were "significantly symptomatic." In this age
group, they reported, "most hospitalized patients who test positive for
SARS-CoV-2 are asymptomatic or have a reason for hospitalization other
than coronavirus disease 2019."
The authors of the V.A. study note that "most of the data are from
months before the more-transmissible delta variant became dominant." But
they add that "proportions of patients with moderate-to-severe
respiratory distress or being treated with dexamethasone did not appear
to be rising at the end of the observation period (6/30/2021), when
delta was becoming predominant nationwide, suggesting stability of the
vital signs metric for identifying moderate-to-severe COVID-19."
As David Zweig notes in The Atlantic, the V.A. study "demonstrates that
hospitalization rates for COVID, as cited by journalists and policy
makers, can be misleading, if not considered carefully. Clearly many
patients right now are seriously ill. We also know that overcrowding of
hospitals by COVID patients with even mild illness can have negative
implications for patients in need of other care. At the same time, this
study suggests that COVID hospitalization tallies can't be taken as a
simple measure of the prevalence of severe or even moderate disease,
because they might inflate the true numbers by a factor of two."
Zweig interviewed Shira Doron, a co-author of the V.A. study who is an
infectious disease specialist and epidemiologist at Tufts Medical
Center. "As we look to shift from cases to hospitalizations as a metric
to drive policy and assess level of risk to a community or state or
country," she told him, "we should refine the definition of
hospitalization. Those patients who are there with rather than from
COVID don't belong in the metric."
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