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10 Coronavirus Immunity & Antibodies

Everything we know about

coronavirus immunity and

antibodies — and plenty

we still don’t

By Andrew Joseph

People who think they’ve been exposed to the
novel coronavirus are clamoring for antibody
tests — blood screens that can detect who has
previously been infected and, the hope is, signal
who is protected from another case of Covid-19.

But as the tests roll out, some experts are trying
to inject a bit of restraint into the excitement that
the results of these tests could, for example,
clear people to get back to work. Some antibody
tests have not been validated, they warn. Even
those that have been can still provide false “Right now, we have no evidence that the use of think they’re protected from the virus when they
results. And an accurate positive test may be a serologic test can show that an individual is have yet to have an initial infection.
hard to interpret: the virus is so new that immune or is protected from reinfection,” the
researchers cannot say for sure what sort of
WHO’s Maria Van Kerkhove said at a briefing Serology testing “isn’t a panacea,” said Scott
results will signal immunity or how long that last week. Becker, the CEO of the Association of Public
armor will last. Health Laboratories. “When it’s used, we need

Below, STAT looks at the looming questions to ensure there are good quality tests used.”
They caution that policymakers may be making about antibodies and immunity that scientists are
sweeping economic and social decisions —
racing to answer. One specific concern with antibody tests for
plans to reopen businesses or schools, for SARS-CoV-2: they might pick up antibodies to
example — based on limited data, assumptions,
What are antibody tests? How widely other types of coronaviruses.
and what’s known about other viruses. President
available are they? And how accurate?
Trump last week unveiled a three-phased Globally, there have only been a few thousand
approach to reopen the country; he said some people exposed to the other coronaviruses that
The tests look for antibodies in the blood.
states that have seen declining case counts could
Because antibodies are unique to a particular have caused outbreak emergencies, SARS and
start easing social distancing requirements MERS. But there are four other coronaviruses
pathogen, their presence is proof the person was
immediately. And some authorities have raised that circulate in people and cause roughly a
infected by the coronavirus and mounted an
the idea of granting “immunity passports” to quarter of all common colds. It’s thought that
immune response. The hope is that the presence
people who recover from the virus to allow them just about everyone has antibodies to some
of the antibodies is an indication that the person
to return to daily life without restrictions.
is protected from another infection. combination of those coronaviruses, so
serological tests for SARS-CoV-2 would need to
“Before we embark on huge policy decisions, be able to differentiate among them.
These are different from the tests used to
like issuing immunity certificates to get people
diagnose active infections, which look for pieces
back to work, I think it’s good that people are
of the virus’ genome. What can be gleaned from serological
saying, ‘Hold up, we don’t know that much
results?
about immunity to this virus,’” said Angela
Commercial antibody tests are starting to appear
Rasmussen, a Columbia University virologist.
on the market, but so far, the Food and Drug Detecting antibodies is the first step.
Administration has only cleared a few through Interpreting what they mean is harder.
To be clear, most experts do think an initial
Emergency Use Authorizations. And already,
infection from the coronavirus, called SARS-
health regulators are warning that the ones on Typically, a virus that causes an acute infection
CoV-2, will grant people immunity to the virus
the market may vary in their accuracy. will prompt the body’s immune system to start
for some amount of time. That is generally the
churning out specific antibodies. Even after the
case with acute infections from other viruses,
“I am concerned that some of the antibody tests virus is cleared, these “neutralizing” antibodies
including other coronaviruses.
that are on the market that haven’t gone through float around, ready to rally a response should
FDA scientific review may not be as accurate as that virus try to infect again. The virus might
With data limited, “sometimes you have to act
we’d like them to be,” FDA Commissioner infect a few cells, but it can’t really gain a
on a historical basis,” Anthony Fauci, the head
Stephen Hahn said on “Meet the Press” earlier toehold before the immune system banishes it.
of the National Institute of Allergy and
this month. He added that “no test is 100% (This is not the case for viruses that cause
Infectious Diseases, said in a webcast with
accurate, but what we don’t want are wildly chronic infections, like HIV and, in many cases,
JAMA this month. “It’s a reasonable assumption
inaccurate tests.” hepatitis C.)
that this virus is not changing very much. If we
get infected now and it comes back next
Even the best tests will generate some false “The infection is basically stopped in its tracks
February or March we think this person is going
positives (identifying antibodies that don’t before it can go anywhere,” said Stephen
to be protected.”
actually exist) and some false negatives (missing Goldstein, a University of Utah virologist. But,
antibodies that really are there). Countries Goldstein added, “the durability of that
Still, the World Health Organization has stressed
including the U.K. have run into accuracy issues protection varies depending on the virus.”
that the presumed immunity can only be proven
with antibody tests, slowing down their efforts
as scientists study those who have recovered for
for widespread surveys. (Continued on Page 11)
longer periods. The agency is working on
guidance for interpreting the results of antibody
The fear in this case with imprecise tests is that
tests, also called serologic tests. THANK YOU FIRST RESPONDERS AND
false positives could errantly lead people to
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