by Dr. Joseph Mercola
There are three types of COVID-19 tests: molecular,
antigen and antibody. Molecular and antigen tests
detect active infections, whereas the antibody test
will tell you if you've developed antibodies in
response to a previous SARS-CoV-2 infection
There are seven different coronaviruses known to
cause respiratory illness in humans. The antibodies
created by these different coronaviruses appear very
similar, and recovering from the common cold may
trigger a positive antibody test for COVID-19, even
if you were never infected with SARS-CoV-2
While experts at the Mayo Clinic claim
cross-reactive antibody tests were an early problem
that has been corrected and eliminated, the CDC has
not confirmed this
A Singaporean study found common colds caused by the
betacoronaviruses OC43 and HKU1 appear to make you
more resistant to SARS-CoV-2 infection, and that the
resulting immunity might last as long as 17 years
Other studies suggest immunity after COVID-19
infection may only last between two and 12 months
Right now, there are three types of
COVID-19 tests: 1
Molecular - Also
known as a
PCR (polymerase chain reaction) test, this test
detects whether genetic material of the virus is present in
the sample collected from your throat or sputum (the back of
Antigen - This
test, sometimes referred to as "rapid test," detects viral
Antibody - Also
known as a serology test, it detects the presence of
antibodies in your blood
The first two, molecular
and antigen, are so-called "viral tests" that detect active
infections, whereas the antibody test will tell you if you've
developed antibodies in response to a previous coronavirus
It typically takes your body one to three weeks after an
infection clears to start making antibodies against the virus in
Common Cold Can Trigger Positive COVID-19 Antibody Test
Each of these COVID-19 tests have their issues and controversies.
The problem with antibody testing is that there are seven different coronaviruses known to cause respiratory illness in humans.
Four of them cause
symptoms associated with the common cold:
In addition to the common
cold, OC43 and HKU1 - two of the most commonly encountered
betacoronaviruses 3 - are also known to cause,
...in all age groups. 4
The other three human coronaviruses
- which are
capable of causing more serious respiratory illness - are:
The tricky part is that
the antibodies created by these different coronaviruses appear very
similar, and the U.S. Centers for Disease Control and Prevention
recovering from the common cold can trigger a positive
antibody test for COVID-19, even if you were never infected with
As explained on the CDC's "Test for Past
Infection" web page: 5
"Antibody tests check
your blood by looking for antibodies, which may tell you if you
had a past infection with the virus that causes COVID-19.
proteins that help fight off infections and can provide
protection against getting that disease again (immunity).
Antibodies are disease specific...
A positive test result shows you may have antibodies from an
infection with the virus that causes COVID-19.
However, there is a
chance a positive result means that you have antibodies from an
infection with a virus from the same family of viruses (called coronaviruses),
such as the one that causes the common cold."
Cross-Reactive Antibody Tests Are Still Being Used
In a July 10, 2020, interview with KTTC news, Mayo Clinic chair of
clinical microbiology, Dr. Bobbi Pritt, said: 6
"Early on we had labs using tests that have not received that [U.S.
Food and Drug Administration] review and some of those tests... may
have given you a false positive and detected the normal coronavirus
that circulates and causes the common cold.
I would say the vast
majority have been extensively tested to show that they do not cross
react and give you false positives due to the common cold
While experts at the Mayo
Clinic claim these cross-reactive antibody tests were an early
problem that has since been corrected and eliminated, the CDC does
not confirm or deny the accuracy of this statement on its "Test for
Past Infection" web page. 7
So, it's unclear whether the antibody tests manufactured and used
today are still capable of delivering a positive result if you were
recently exposed and recovered from the common cold virus.
Back on April 29, 2020, infectious disease specialist and CNN
medical analyst Dr. Kent Sepkowitz noted that,
the common cold antibody and the COVID-19 antibody is a real
challenge scientifically," 8 but that doesn't mean it cannot or
hasn't been done.
On a side note, labs are now reporting a shortage of chemicals and
disposable pipette tips required to perform COVID-19 tests, which
means longer wait times - again.
As Scott Shone, director of the
North Carolina State Laboratory of Public Health, told The New York
Times, 9,10 July 23, 2020,
"It's like Groundhog Day. I feel like I
lived this day four or five months ago," referring back to the early
days of the pandemic when test supplies were in short supply.
May Impart Resilience Against COVID-19
While the CDC warns it's still uncertain whether COVID-19 antibodies
prevents reinfection, or if it does, for how long, researchers in
Singapore have presented evidence 11,12,13 suggesting the
likely to be long-lasting.
They discovered common colds caused by the betacoronaviruses OC43
and HKU1 appear to make you more resistant to SARS-CoV-2 infection,
and that the resulting immunity might last as long as 17 years.
The authors suggest that if you've beat a common cold caused by a
OC43 or HKU1 betacoronavirus in the past, you may have a 50/50
chance of having defensive
T-cells that can recognize and help
As reported by the Daily Mail:
"Scientists have found evidence that some immunity may be present
for many years due to the body's 'memory' T-cells from attacks by
previous viruses with a similar genetic make-up - even among people
who have had no known exposure to Covid-19 or SARS …
Blood was taken from 24 patients who had recovered from COVID-19, 23
who had become ill from SARS and 18 who had never been exposed to
either SARS or COVID-19...
Half of patients in the group with no exposure to either Covid-19 or
SARS possessed T-cells which showed immune response to the animal
betacoronaviruses, COVID-19 and SARS.
This suggested patients'
immunity developed after exposure to common colds caused by betacoronavirus or possibly from other as yet unknown pathogens."
According to the researchers, their findings demonstrate that:
"Virus-specific memory T-cells induced by betacoronavirus infection
are long-lasting, which supports the notion that COVID-19 patients
would develop long-term T-cell immunity.
Our findings also raise the
intriguing possibility that infection with related viruses can also
protect from or modify the pathology caused by SARS-Cov-2."
Added support for these conclusions were published May 14, 2020, in
the journal Cell.
This study 16 found that not only did 70% of
samples obtained from recovered COVID-19 patients have resistance to
SARS-CoV-2 on the T-cell level but so did 40% to 60% of people who
had not been exposed to the virus.
According to the authors, this
"cross-reactive T cell recognition between
circulating 'common cold' coronaviruses and SARS-CoV-2."
Other Researchers Report Low Immunity Post-Recovery
The immunity issue isn't entirely cut and dry, though.
research, which looked at antibody levels in recovered COVID-19
patients in Germany, found they lost their antibodies after two to
"Clemens Wendtner, a chief physician at the hospital, tested
COVID-19 patients for immunity after they had been treated for the
disease at the end of January 2020. The tests showed a significant
decrease in the number of antibodies," DW reported in a July
14, 2020, article. 17
"Wendtner says 'neutralizing' antibodies, which stop a viral attack,
fell in four out of nine of the patients who were tested, within two
to three months. Those findings coincide with a similar
investigation done in China.
That study also found that antibodies in COVID-19 patients do not
persist in the blood. Further research is still required. But these
initial findings suggest that a second infection is possible..."
However, it is important to realize that loss of the ability to
determine antibody levels may not necessarily reflect lack of immune
protection, as there may be innate cell mediated immunity that
provides protection that is not being measured by the humoral
Will COVID-19 Behave Like the Common Cold?
If reinfection is possible, then COVID-19 would behave much like the
common cold and seasonal influenza, which can strike more than once
- if not in a single season, then certainly in any given year.
that's the case, then "immunity passports" and most other COVID-19
interventions, such as school closings and business shutdowns,
become even more questionable than they already are.
If the novel coronavirus behaves like common cold viruses, then talk
of "immunity passports" and herd immunization is pointless.
If SARS-CoV-2 ends up behaving like other human coronaviruses that
cause the common cold, immunity may only last six to 12 months, a
European study 18 says.
Here, they did not look at SARS-CoV-2
antibodies but, rather, antibodies against the other four coronaviruses that cause the common cold, none of which were
BGR, which reported the findings:
"'Frequent reinfections at 12 months post-infection and substantial
reduction in antibody levels as soon as 6 months post-infection'
were observed for those viruses.
If the novel coronavirus behaves the same way, then talk of
'immunity passports' and herd immunization is pointless. A person
who recovered from COVID-19 could get it again in six to 12 months
without another vaccine shot…
The researchers note that the human coronaviruses are 'biologically
dissimilar' and 'have little in common, apart from causing the
But SARS-CoV-2 doesn't have to be similar to any of
them to follow the same immunity pattern."
Is Herd Immunity Against COVID-19 Possible?
The issue of reinfection also raises questions about whether herd
immunity is ever going to be possible.
Studies cited by The Daily
Mail 20 claim herd immunity against COVID-19 could be achieved if
just 10% to 43% of people develop lasting immunity.
This is a far cry from the percentages typically required for
vaccine-induced "herd immunity" (which is really a misnomer, as
vaccine-induced immunity doesn't work like natural immunity, and
herd immunity is really only achieved when enough people recover
from the illness in question).
According to The Daily Mail:
"The concept of herd immunity hinges on people only being affected
once, so that when a certain number of people have been infected
with the virus already it can't spread any more.
It remains a mystery as to whether this is the case for COVID-19
but, if it is, then herd immunity could offer some protection during
a second wave of the disease …
Researchers now say it could work to some extent if only one or two
out of 10 people have been infected naturally and become immune to
Another study has taken a similar line and suggested
herd immunity could develop at around 43 percent of the population
Immunity among the most socially active people,
scientists say, could protect those who come into contact with fewer
1 - KHOU11
June 30, 2020
2 - CDC.gov
Human Coronavirus Types
Infect Dis. 2013 Nov 15; 208(10): 1634–1642
Test for Past Infection, Updated June 30, 2020
6 - KTTC
July 10, 2020
8 - CNN
April 29, 2020
9 - New
York Times July 23, 2020
10 - New
York Times July 23, 2020 (Archived)
11 - Biorxiv
preprint DOI: 10.1101/2020.05.26.115832 (PDF)
12, 14, 15
Mail June 12, 2020
13 - Science
Times June 12, 2020
16 - Cell
May 14, 2020 DOI: 10.1016/j.cell.2020.05.015
17 - DW
July 14, 2020
18 - Researchgate
preprint May 2020 DOI: 10.1101/2020.05.11.20086439
19 - BGR
May 26, 2020
Mail July 14, 2020