By
Alan Mozes HealthDay Reporter
MONDAY,
Nov. 2, 2020 (HealthDay News) -- The coronavirus and the
flu are two entirely different viruses. But a new study
suggests those who get a flu vaccine face a considerably lower
risk for being hospitalized if and when they get COVID-19.
And
the flu vaccine also appears to significantly
reduce a COVID-19 patient's risk for ending up in an intensive care unit (ICU),
researchers say.
The
findings are based on an analysis of electronic health records for 2,000 COVID-19
patients. All had tested positive for the virus at some point between this past
March and August. And just over 10% of the patients had previously been
vaccinated for the flu.
"The
flu and COVID-19 are indeed different disease processes caused by different
viruses," stressed study author Dr. Ming-Jim Yang. "Although some of
the symptoms may overlap between the two
diseases, they potentially have different short-term and long-term
consequences."
It's
also the case that "COVID-19 still has a much higher mortality [rate] than
the flu," Yang noted. And long-term lung, heart and brain problems seen
among surviving COVID-19 patients "do not seem to happen with the flu,"
he added.
Nevertheless,
"our team looked at patients who tested positive for COVID-19 and saw that
patients who received the influenza vaccine within the last year were less
likely to be hospitalized and be admitted to the ICU," Yang said.
How
much less?
"COVID
patients who had not received a flu vaccine within the last
year had 2.4 times greater odds of being hospitalized and 3.3 times greater
chance of being transferred to the ICU," said Yang, a third-year resident
in family medicine in the department of community health and family medicine at
the University of Florida in Gainesville.
As
to how a vaccine for an entirely different virus might offer such protection,
Yang said the jury is still out. Also, the study did not prove that a flu
vaccine actually caused the risk of severe COVID-19 to drop, just that there
was an association.
"Unfortunately,
we do not know why the flu vaccine would have this beneficial side
effect," he said. "Our study did not look at this specifically. [But]
if one looks at the available scientific studies, we can guess that the flu
vaccine might increase natural killer cell activity, a type of immune cell that
has been shown to target cancer and cells infected by viruses."
The
flu vaccine may also stimulate a patient's immune system to step up and fight off
COVID-19 more quickly and rigorously than otherwise, Yang added.
That
point was echoed by Dr. Michael Niederman, associate division chief and
clinical director of pulmonary and critical care at NewYork-Presbyterian/Weill
Cornell Medical Center, in New York City.
"Flu
shots can stimulate specific antiviral immunity [to the flu]," he noted,
"as well as nonspecific 'innate immunity.' It's that latter effect that
might end up conferring added protection against the most serious outcomes
among COVID patients," Niederman said.
It's
also the case that just avoiding getting the flu -- by means of a flu shot --
can help preserve a patient's immune system readiness, said Chunhuei Chi,
director of Oregon State University's Center for Global Health.
"One
thing we do know is that flu shots are effective in preventing flu," Chi said.
"And when a person is infected with the flu, her/his immune system will be
weakened. Under such conditions, the person is more vulnerable to infection
with COVID-19 and, if infected, [outcomes] tend to be more serious."
Chi
also noted that, "on average, those who get flu shots tend to be people
who are more cautious and care about their own health. These are the same
people who are more likely to [adopt] a higher level of safety-hygiene
practices during the pandemic," which could mean that their future
COVID-19 exposure might be to a "lower density of virus."
Niederman
broadly agreed, suggesting that those who get vaccinated against the flu are
already likely at lower risk for getting COVID-19.
People
who get a flu shot "are also the same people who are likely to follow
other preventive care advice, such as wearing
masks and social distancing. It is the latter that
prevents COVID, not the flu shot itself," Niederman said.
Whatever
the explanation, the latest finding seems to offer yet another incentive to get
a flu shot.
Yang
said, "The fact is that the benefit seems to exist. More studies will be
needed to look at what the mechanism behind the benefit is."
He
and his colleagues reported their findings online Oct. 29 in the Journal
of the American Board of Family Medicine.
There's
more on the overall benefits of the flu vaccine at the U.S. Centers for Disease Control and Prevention.
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