Don't Rely on Antibody Testing to Assess COVID-19 Immunity

You'll hear misconceptions about SARS-CoV-2 antibody tests.

These serology tests are intended to identify a recent or prior COVID-19 infection.

Now more patients want to know if they have antibodies...especially after COVID-19 vaccination.

But reinforce that these antibody tests are NOT designed to assess if patients are protected against COVID-19.

Explain why fully vaccinated patients may still test negative.

For example, patients who've had COVID-19 develop IgG and IgM antibodies in response to various targets...including the SARS-CoV-2 spike protein and nucleocapsid protein.

But current COVID-19 vaccines only trigger antibodies to the spike protein...and some antibody tests don't detect these.

Don't recommend another COVID-19 vaccine dose if fully vaccinated patients test negative.

And tell patients who've had COVID-19 not to be surprised if a test suggests they don't have antibodies. False negatives could be due to timing of the test, dropping antibody levels, or other factors.

Also point out that a POSITIVE antibody test doesn't guarantee a patient's immune...especially if they're unvaccinated.

That's because some evidence suggests that antibodies may last at least 6 months after COVID-19 infection...but it's still too soon to say what level is needed to protect against getting COVID-19 again.

In general, advise saving antibody testing to help answer whether COVID-19 may be the cause of "long-haul" symptoms (fatigue, myalgia, etc) lasting for weeks, despite negative viral tests.

Explain that there aren't any OTC antibody tests yet. But several are authorized for use in pharmacies under a CLIA waiver.

Sort through rapid testing options, including diagnostic tests, in our COVID-19 Point-of-Care Testing chart.

And see our FAQ, Communicating About COVID-19 Vaccination, for more talking points about antibody testing.

Key References

  • www.fda.gov/medical-devices/safety-communications/antibody-testing-not-currently-recommended-assess-immunity-after-covid-19-vaccination-fda-safety (6-21-21)
  • www.cdc.gov/coronavirus/2019-ncov/lab/resources/antibody-tests-guidelines.html (6-21-21)
  • www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/eua-authorized-serology-test-performance (6-21-21)
Pharmacist's Letter. July 2021, No. 370702



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