DO COVID-19 VACCINATIONS CAUSE FALSE POSITIVES?

Currently the CDC recommends that any fully vaccinated person who experiences symptoms consistent with COVID-19 be tested for SARS-CoV-2 if indicated1. That leads to the question can COVID-19 vaccinations cause false positives?  Here’s what we know.

Flu Vaccination with Live Attenuated Influenza Virus Can Yield False Positives

False positives after receiving a seasonal influenza vaccination are linked to vaccinations that use live, attenuated viruses. According to the CDC, false positive influenza testing results can occur in people who recently received intranasal administration of live attenuated influenza virus vaccine (LAIV). Since the nasal passages are infected with live influenza virus vaccine strains during LAIV administration, sampling the nasal passages within a few days after LAIV vaccination can yield positive influenza testing results. It may be possible to detect LAIV vaccine strains up to 7 days after vaccination, and in rare situations, for longer periods3. Live vaccines can generate false-positive results, can threaten the integrity of epidemiological data and may misdirect treatment and control efforts. This has not been reported with other forms of seasonal influenza vaccinations.

CDC Does not Expect Vaccinations to Produce False Positive COVID-19 Tests

The COVID-19 vaccines do not use live attenuated virus. According to the CDC, neither the recently authorized and recommended vaccines nor the other COVID-19 vaccines currently in clinical trials in the United States can cause someone to test positive on viral tests, which are used to see if you have a current infection.​ However, vaccinated individuals may test positive on some antibody tests2, which are blood tests used to see if someone has mounted an immune response to SARS-CoV-2.

References:

  1. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/fully-vaccinated-guidance.html
  2. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/facts.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fcoronavirus%2F2019-ncov%2Fvaccines%2Fvaccine-benefits%2Ffacts.html
  3. https://www.cdc.gov/flu/professionals/diagnosis/clinician_guidance_ridt.htm

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