COVID-19 Antibody Testing and Immunity
Posted June 5, 2020 by UVM Health Network
There has been much discussion in the media on the use of serology (antibody) testing in combating the COVID-19 pandemic. Some of this information is misleading, setting unrealistic expectations on how we could use testing to re-open the economy, or identify a person's COVID-19 immunity status. To debunk some of the myths surrounding this test, and to better explain why we are restricting the use of this test in our patient community, we are providing you with realistic expectations on the use and limitations of COVID-19 serology testing.
What is serologic (antibody) testing?
When you get sick with a virus, your immune system produces antibodies to that virus. It is your body's way of protecting you and preventing future infections from the same virus, bacteria or parasite. Medical professionals use serologic testing to detect the presence of antibodies from COVID-19 telling them whether you had COVID-19 at some point. However, this type of serologic test is not able to detect an active virus – only an infection that happened in the past.
Does a serology (antibody) test tell me if I am immune to COVID-19?
Many think that a positive antibody test to COVID-19 suggests immunity or protection from future infection by the virus. Unfortunately, it is too early in our knowledge of COVID-19 to know if antibodies are protective, how long they last, or how they impact your ability to infect others. Early data suggests that the development and the effectiveness of antibodies may depend on age, overall health, and severity of COVID-19 related illness.
Why is UVM Health Network restricting serology (antibody) testing?
We are restricting this test with our patients because the test does not provide clear or accurate information about your body's immunity to COVID-19 and does not provide us with information to guide your behaviors or inform your choices during this pandemic. This test has limited clinical utility at this time as given in our recommendations below.
Our recommendations are as follows:
- Do not use antibody testing to acutely diagnose COVID-19 infection.
- Do not use antibody testing results to determine a person's COVID-19 immunity status, return-to-work decisions, use of masks or other personal protective equipment, or safety of vulnerable persons to go into public.
- A positive antibody test only tells you that you were infected with COVID-19 in the past.
- Antibody testing is useful for understanding how many people COVID-19 has infected. It's also useful for identifying children presenting with Pediatric Multi-System Inflammatory Syndrome associated with COVID-19 (MIS-C) and evaluating convalescent plasma donors.
- Interpret antibody testing results with an awareness of the prevalence of COVID-19 in your community and the false positive rate of any given test.
We are all eager to develop a solution to this pandemic, but serology testing is not our silver bullet. Instead, we need to continue to practice safe and healthy behaviors like social distancing, handwashing, and mask-wearing as our communities slowly reopen. Our behaviors will determine our ability to return to a sense of normalcy. Stay the course, stay informed, and most importantly, stay safe.
Clayton Wilburn, MD, DABCC, is the director of Clinical Chemistry, Immunology, and Point-of-Care Testing in the Department of Pathology & Laboratory Medicine at the University of Vermont Medical Center and Assistant Professor of Pathology and Laboratory Medicine at UVM Larner College of Medicine.