COVID-19 antibody study shows downside of not receiving second shot
Recovering from COVID-19 doesn't guarantee antibodies or confer immunity
to re-infection, study finds

Date:
August 30, 2021
Source:
Northwestern University
Summary:
A new study shows that two months after the second Pfizer/Moderna
vaccination, antibody response decreases 20 percent in adults
with prior cases of COVID-19, and tests how well current vaccines
resist emerging variants. The study also showed that prior exposure
to SARS-CoV-2 does not guarantee a high level of antibodies, nor
does it guarantee a robust antibody response to the first vaccine
dose. This directly contradicts the assumption that contracting
COVID will naturally make someone immune to re-infection. The
findings further support vaccination (and two doses), even for
people who have contracted the virus previously.



FULL STORY ==========================================================================
A new study shows that two months after the second Pfizer/Moderna
vaccination, antibody response decreases 20% in adults with prior cases
of COVID-19. The study also tests how well current vaccines resist
emerging variants.


==========================================================================
The Northwestern University study underscores the importance of receiving
a second dose of vaccine, not only because it is commonly known that
immunity from vaccines wanes over time, but also because of the risk
posed by emerging variants, including the highly contagious delta variant.

The study also showed that prior exposure to SARS-CoV-2 does not
guarantee a high level of antibodies, nor does it guarantee a robust
antibody response to the first vaccine dose. This directly contradicts the assumption that contracting COVID will naturally make someone immune to re-infection. The findings further support vaccination (and two doses),
even for people who have contracted the virus previously.

A team of scientists, including biological anthropologist Thomas McDade
and pharmacologist Alexis Demonbreun, tested blood samples from adults
who had tested positive for SARS-CoV-2 to measure how long the immunity benefits of Pfizer and Moderna vaccines last and how well they protect
from newer variants.

Study participants were selected from a racially and ethnically diverse community-based sample of Chicago-area adults recruited at the start of
the pandemic. Using at-home antibody testing kits developed in the lab, participants submitted blood samples two to three weeks after their
first and second dose of vaccination and two months after the second dose.

Antibody response after second shot In the lab, the researchers tested
for neutralizing antibodies by measuring whether the blood sample could
inhibit the interaction between the virus' spike protein and the ACE2
receptor -- this interaction is how the virus causes an infection once
it enters the body.



========================================================================== "When we tested blood samples from participants collected about three
weeks after their second vaccine dose, the average level of inhibition
was 98%, indicating a very high level of neutralizing antibodies,"
said McDade, professor of anthropology in the Weinberg College of Arts
and Sciences and a faculty fellow with the University's Institute for
Policy Research.

The scientists tested emerging variants B.1.1351 (South Africa), B.1.1.7
(UK) and P.1 (Brazil) and found the level of inhibition to viral variants
was significantly lower, ranging from 67% to 92%.

Antibody response declined after two months In testing samples collected
two months after the second dose, they found antibody responses declined
by about 20%.

The researchers found that the antibody response to vaccination varied
based on history of prior infection.



========================================================================== Individuals with clinically confirmed cases of COVID-19 and multiple
symptoms had a higher level of response than those who tested positive
but had mild symptoms or were asymptomatic.

"Many people, and many doctors, are assuming that any prior exposure
to SARS- CoV-2 will confer immunity to re-infection. Based on this
logic, some people with prior exposure don't think they need to get
vaccinated. Or if they do get vaccinated, they think that they only need
the first dose of the two-dose Pfizer/Moderna vaccines," McDade said.

"Our study shows that prior exposure to SARS-CoV-2 does not guarantee a
high level of antibodies, nor does it guarantee a robust antibody response
to the first vaccine dose. For people who had mild or asymptomatic
infections, their antibody response to vaccination is essentially the same
as it is for people who have not been previously exposed." McDade adds
that although the research was conducted prior to the emergence of the
delta virus, the conclusions are similar.

"As far as protection goes after vaccination, the story is the same for
all the variants, including delta -- the vaccine provides good protection,
but not as good protection as the original version of the virus for which
the vaccine was designed. Combine that with the fact that immunity wanes
over time, you get increased vulnerability to breakthrough infection.

"So, it's two strikes right now -- delta plus waning immunity among the
first wave of the vaccinated," McDade said.

The study "Durability of antibody response to vaccination and surrogate neutralization of emerging variants based on SARS-CoV-2 exposure history"
is published in the journal Scientific Reports.

========================================================================== Story Source: Materials provided by Northwestern_University. Original
written by Stephanie Kulke. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Thomas W. McDade, Alexis R. Demonbreun, Amelia Sancilio, Brian
Mustanski,
Richard T. D'Aquila, Elizabeth M. McNally. Durability of antibody
response to vaccination and surrogate neutralization of emerging
variants based on SARS-CoV-2 exposure history. Scientific Reports,
2021; 11 (1) DOI: 10.1038/s41598-021-96879-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210830081803.htm

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