Progress in the U.S. has been slower, though Governors including New York’s Andrew Cuomo, researchers and hospitals are eager to accelerate testing. The Food and Drug Administration last month issued emergency guidance permitting companies to launch antibody tests that have been internally validated as long as they cage results with numerous caveats to patients. These include that the test hasn’t been reviewed by the FDA, a negative result doesn’t rule out infection and “positive results may be due to past or present infection with non-SARS-CoV-2 coronavirus strains.”

Forty some companies have indicated that they plan to launch tests. But many are waiting for the government imprimatur of FDA approval and inoculation against lawsuits. Some caution about antibody tests is understandable. Tests must be specific and sensitive—i.e., detect an antibody particular to Covid-19 when present and not other antibodies. A false positive antibody result is more worrisome than a false coronavirus diagnosis since people who mistakenly believe they are immune could spread the virus.

This is why it’s important that antibody tests be validated for accuracy. But once they are, the FDA should ensure they can be distributed more quickly and broadly than the diagnostic tests have been.