More coronavirus anti-body tests are coming out, but officials say more testing needs to be done before they are put into widespread use.

The tests are different from the tests used to find if someone is sick with the virus. Rather, the tests look for the antibodies in a person's blood that indicate an individual’s immune system has responded to an infection.

The tests could be particularly helpful in determining when a person can safely return to work.

However, officials say the finger-prick tests don't require FDA approval for sale, but warn they can’t be trusted without independent testing. “Having an inaccurate test is worse than having a test,” says FDA Commissioner Dr. Stephen M. Hahn.

Labs across the country are conducting their own experiments to ensure the tests work as promised. U.S. regulators say there are at least 70 companies making such tests.