Why experts are questioning COVID-19 antibody testing results

Coronavirus

ROCHESTER, N.Y. (WROC) — The U.S. Food and Drug Administration is advising against the use of COVID-19 antibody test results to evaluate immunity and protection from the coronavirus after vaccination or illness.

This recommendation is consistent with CDC guidance.

Dr. Jeff Harp of Highland Family Medicine explained why Tuesday during News 8 at Sunrise.

On May 19, 2021, the U.S. Food and Drug Administration (FDA) advised against the use of SARS-CoV-2 antibody test results to evaluate immunity or protection from COVID-19 after vaccination or illness, consistent with CDC guidance. Why is that?

Currently authorized SARS-CoV-2 antibody tests have not been evaluated to assess the level of protection provided by an immune response to COVID-19 vaccination. A positive result from a SARS-CoV-2 IgG antibody test in a person who is not fully vaccinated against COVID-19 does not necessarily indicate long-term immunity or protection from COVID-19. And a negative or low result from a SARS-CoV-2 IgG antibody test in a person who is fully vaccinated against COVID-19 does not indicate insufficient vaccine-induced immunity.

But what if a person had an antibody test done already? Should the results change their immunization schedule?

No. People with an incomplete COVID-19 vaccine series (i.e., receipt of a single dose of a 2-dose series) should complete the vaccine series as recommended by the CDC, regardless of the results of post-vaccination serologic testing. No additional doses of COVID-19 vaccine are recommended on the basis of postvaccination serologic test results for people who are fully vaccinated against COVID-19 (≥2 weeks after receipt of the second dose in a 2-dose series (Pfizer-BioNTech and Moderna) or ≥2 weeks after receipt of the single dose of the Janssen vaccine). People with a history of prior COVID-19 infection should be offered the COVID-19 vaccine regardless of the results of pre-vaccination serologic tests. This recommendation applies to people who experience SARS-CoV-2 infection before receiving any vaccine dose and those who experience SARS-CoV-2 infection after the first dose of an mRNA vaccine but before receipt of the second dose.

So what good are the antibody tests?

SARS-CoV-2 antibody tests play an important role in assessing whether patients have had a current or recent COVID-19 infection. However, currently available SARS-CoV-2 antibody tests have not been evaluated to assess the immunity induced by COVID-19 vaccination. Antibody tests only tell whether a person has been exposed to COVID-19 RNA, not how much immunity resulted from that exposure.

What is the bottom line here?

At this time antibody testing is not useful in deciding who needs to be vaccinated or what vaccine to use. All eligible people should be vaccinated according to current guidelines. Remember that 70 to 90 percent of all Americans must be immunized to protect all of us adequately.

Copyright 2021 Nexstar Media Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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