What to know about antibody tests in a post-vaccine world

The CDC is warning against using commercial tests to determine immunity.

A Centers for Disease Control and Prevention panel once again warned consumers this week not to use commercial antibody tests to check whether or not they are immune to COVID-19. These tests, the panel said Thursday, are not consistent and can't be used to measure protection against the virus. Antibody testing is primarily used to determine if a person has previously been infected with the COVID-19 virus. Early reports suggested that people who tested positive for antibodies after either a known or asymptomatic infection had some level of immunity. Now, most health officials agree that having a positive antibody test does not mean a person is immune to contracting the virus. "Antibodies after a period of time start to come down again, that's not a bad thing," said Dr. Todd Ellerin, director of infectious diseases at South Shore Health. But the presence of antibodies is only part of the story when it comes to immunity. "Your antibodies are only one part of the immune system. You have other parts of the immune system as well, such as T-cells," said Ellerin. "T-cell response is probably very important to protecting against severe disease because they can attack the virus directly."