Antibodies are identified in the blood of individuals who have been previously infected with or
immunized against a virus that causes a disease; they indicate the body’s efforts (past infection)
or readiness (past infection or vaccination) to combat a particular virus. Once produced,
antibodies may provide protection against infection or severe illness for an extended period of
time. Antibodies, whether they are the result of an illness or vaccination, decline with time. The
rate at which antibodies decline varies by disease and by individual.
SARS-CoV-2, the virus that causes COVID-19, is young, and our understanding of it has rapidly
evolved. This data will be updated as new information becomes available. Until scientists have
more information on how long antibodies against SARS-CoV-2 protect against contracting
SARS-CoV-2 or becoming extremely unwell with COVID-19:
Individuals who are not immunized should be vaccinated.
Individuals who are current on their vaccinations should adhere to the CDC’s Recommendations
for Staying Current on Vaccinations.
Everyone should continue to take precautions to safeguard oneself and others.
A positive antibody test reveals that a person possesses COVID-19 antibodies because:
● Prior exposure to SARS-CoV-2 or
● Vaccination against COVID-19
Antibody exam
The external icon should not be utilized to diagnose a present infection. An antibody test may
not detect a current illness because it can take 1 to 3 weeks for the body to produce antibodies
following an infection.
Antibodies are a sign of protection and frequently aid in preventing infections; nevertheless,
some individuals with antibodies may become reinfected (infected again after recovering from a
previous illness) or infected after immunization.
Antibodies may avert severe sickness, hospitalization, and death in some situations.
Healthcare practitioners that utilize antibody tests must be familiar with the information provided
by various tests and how to interpret test findings.
If a person is tested for antibodies after getting a vaccine, some (but not all) antibody tests may
yield a positive result.
Antibody testing is currently not suggested to determine COVID-19 immunity following
vaccination.
The accuracy of tests with FDA Emergency Use Authorization varies. In this Independent
Evaluation of SARS-CoV-2 Antibody Test Performance, the performance features of serological
tests are described.
False-positive results occur when the test indicates the presence of SARS-CoV-2 antibodies
when these antibodies are not present.
False-negative results occur when the test is negative for SARS-CoV-2 antibodies despite the
presence of these specific antibodies.
By selecting an antibody test with a high level of specificity and testing individuals who are likely
to have had COVID-19 or are known to have been vaccinated, false-positive findings can be
reduced.
The Interim Guidance for COVID-19 Antibody Testing in Clinical and Public Health Settings
provides thorough information on utilizing antibody tests most effectively.
Positive antibody test results allow a person to resume normal activities, including work, but
they should still take precautions to protect themselves and others, such as getting vaccinated.
The findings of an antibody test should not be used to evaluate a person’s ability to return to
work or education.
Generally speaking, antibody tests should not be used to diagnose an active infection with the
virus that causes COVID-19. Because it can take 1 to 3 weeks for the body to produce
antibodies following an infection, an antibody test may not detect a present illness.
Antibody test results should not be used to group people in schools, dorms, and prisons or
exempt someone from screening tests.
Even if they test positive for SARS-CoV-2 antibodies, individuals who use personal protective
equipment (PPE) at work based on a site-specific risk assessment for the task being performed
should continue to wear PPE.
If a person has COVID-19 symptoms or a suspected or proven exposure to someone with
COVID-19, they should receive a virus test (NAAT or antigen) to determine if they are currently
infected.
Timing
The test’s validity will also rely on how recently a patient contracted COVID-19. It takes time for
the immune system to generate antibodies in sufficient quantities for detection. According to the
Cochrane analysis, only 30% of persons who take an antibody test one week after exhibiting symptoms will test positive. This increases with time – to 70 percent by the second week and 90
percent by the third – but may decrease as antibody levels decline. Moreover, if a person
develops a minor case of COVID-19 or does not exhibit any symptoms, they may not create
enough antibodies for the test to detect them.
Cross-reactivity
Antibodies generated in response to other coronaviruses, such as the virus that causes the
common cold, may have a structure remarkably similar to antibodies against SARS-CoV-2. This
indicates that these antibodies in the blood may be sufficient to generate a positive test result,
even in individuals who have never been infected with COVID-19. It is feasible that this
commonality will work in our favor and also mean that these antibodies provide some protection
against COVID-19, but additional evidence is required to confirm this.
Antibodies = defense
Even considering all of these characteristics, it is still unclear if screening for antibodies is a
reliable technique to determine whether a person is immune to COVID-19 or how long this
immunity might remain. Antibodies are only one component of a complicated immune response
triggered by SARS-CoV-2 infection. The absence of antibodies does not indicate that the
immune system is not ready to respond to reinfection in other ways. The existence of antibodies
suggests that they are present in sufficient quantities to protect against reinfection.
There is a time and a place for antibody testing. They can provide information that helps
scientists forecast future transmission of the virus by assessing what percentage of the
population remains at risk or identifying areas where communication is especially prevalent.
This will support target vaccination efforts, which will be especially crucial given the expected
limited supply of COVID-19 vaccinations if and when they become available. Antibody tests
could also be utilized to identify individuals who could give blood containing antibodies to treat
individuals with a life-threatening case of COVID-19. However, for everyone who receives an
antibody test, placing too much weight on the outcome is hopeful and, at worst harmful.
