Antibody testing has become an important topic in the country’s COVID-19 response. An antibody test checks a person’s blood by looking for antibodies, which show if you had a previous infection with COVID-19. Although DHEC does get laboratory reports for every antibody test completed on a patient, regulation and approval of these tests is done by the U.S. Food and Drug Administration (FDA).
Early in the pandemic response, on March 16, the FDA issued a policy relaxing its regulations to make it easier for companies to develop and offer novel coronavirus antibody tests for clinical and population level use without needing to supply the FDA with validation data indicating the accuracy of their results. This early flexibility allowed more companies, laboratories, and universities to develop different antibody tests that could then be used to identify a subset that proved to be more reliable.
On May 4, the FDA made important changes to the March 16 policy, requiring commercial manufacturers to submit validation data to the FDA within 10 days in order to be considered for Emergency Use Authorization (EUA) of their test. In addition, the FDA used data collected previously to set performance thresholds for these tests. At this time, every test available in the clinical setting should have EUA.
Based on information from the CDC, DHEC advises that these tests provide limited information to patients about whether or not they had a past COVID-19 infection. Since May 14, positive antibody tests can reliably confirm if someone has had a past infection. They are less reliable in determining if someone is currently infected and should not be used as the only test to make a current diagnosis of COVID-19. We do not know if a positive antibody test as a result of a previous infection offers any protection against a second infection. It will be many months before we can feel reassured that a previous infection offers us an adequate level of protection to keep us safe. People who have a positive or negative antibody test should continue to practice physical distancing and wear a mask when in public or in a group to protect themselves and others.
Please see additional information about COVID-19 antibody testing below.
I am unvaccinated and have tested positive for COVID-19 antibodies. Do I have to quarantine after close contact with someone who is infected with COVID-19?
Unvaccinated persons who have tested antibody positive within 3 months before or immediately following an exposure to someone with suspected or confirmed COVID-19 and who have remained asymptomatic since the current COVID-19 exposure do not need to quarantine in low-risk situations.
- Low risk situations include settings where contact with persons at high risk of COVID-19 severe illness is not anticipated for at least 10 days following exposure. Persons of high risk include older adults and persons with certain medical conditions.
Individuals should still monitor themselves for symptoms of COVID-19 during the 14 days after exposure and if symptoms of COVID-19, develop they should isolate and seek testing.
Additional information about FDA approved antibody tests can be found here.
Will DHEC’s Public Health Laboratory offer antibody tests for COVID-19?
Our Public Health Laboratory does not plan to offer this testing at this time.
Does the presence of antibodies to COVID-19 mean the patient is infected?
Not necessarily. It may indicate a past infection that has been cleared or a current infection which began within the past week or two.
Does the presence of antibodies to COVID-19 mean the patient is no longer contagious?
No, patients can still be shedding infectious virus even though they have an antibody response. It also doesn’t mean that they are immune because we don’t know if their antibodies are enough to keep someone immune or for how long.
Does the presence of antibodies to COVID-19 mean the patient is immune to reinfection?
We don’t know that yet. The antibody tests do not indicate whether the antibodies are protective or not.
Are there any disadvantages or concerns with using the antibody tests, even the approved tests?
Patients who are told their antibody test is negative may decrease social distancing efforts, thinking they are not infectious. This could be dangerous because person with a negative antibody test is still vulnerable to becoming infected. The person could also already be infected and shedding virus to other people but not have developed antibodies yet.
Those who are told they have positive antibodies may feel that they are now “immune” from becoming infected with COVID-19 because they already had the virus although this has not been proven. This could lead people to feel safe in crowds and not take adequate precautions. Some people have tested positive for COVID-19 for a second time after already recovering from a previous infection.
Can we use antibody test to determine if an employee can go back to work?
Because the antibody test does not give information on the infectious status, or immunity from the disease, it is not useful for this purpose. We refer to the latest CDC guidance for when infected employees may return to work.