COVID-19: Don’t Rely on Antibody Test After Vaccination

Scientists believe that COVID-19 antibodies develop within 1 to 3 weeks after infection. Antibodies are the proteins your body produces in response to an infection, and lab tests will detect these antibodies if your body fought that pathogen. A positive antibody test for COVID-19 means that you were infected with SARS-CoV-2, which is the virus that causes COVID-19 whether you had symptoms or not.

Titer blood tests measure antibodies in your blood, and they can be used as proof of immunity to a disease. This is why proof of a prior diagnosis with measles, mumps, or chickenpox is allowed for a child to be enrolled in a U.S. public school. If the child has the antibodies, then proof of vaccination is unnecessary.

However, the FDA issued a safety warning about COVID-19 in May 2021. It warned the public and health care providers not to use SARS-CoV-2 antibody tests to gauge immunity, especially with people who have received the COVID-19 vaccine.

FDA Recommends not using antibody test to determine COVID-19 immunity

In this communication, the FDA stated, “results from currently authorized SARS-CoV-2 antibody tests should not be used to evaluate a person’s level of immunity or protection from COVID-19 at any time, and especially after the person received a COVID-19 vaccination.”

They further state, ““more research is needed in people who have received a COVID-19 vaccination.” The SARS-CoV-2 antibody tests haven’t been studied to determine the level of protection they confer on people who have received the vaccine. The FDA also stated that a positive antibody test doesn’t prove immunity, only that you were possibly infected by the virus.