The Food and Drug Administration (FDA) on Tuesday warned that antigen tests may be less effective in detecting the highly contagious omicron variant of COVID-19.
"Early data suggests that antigen tests do detect the omicron variant but may have reduced sensitivity," the FDA announced.
"The FDA continues to authorize the use of these tests as directed in the authorized labeling and individuals should continue to use them in accordance with the instructions included with the tests," the announcement added. "Antigen tests are generally less sensitive and less likely to pick up very early infections compared to molecular tests."
The agency also recommended a follow-up molecular test for people who are "experiencing symptoms or have a high likelihood of infection due to exposure" even if they have tested negative with an antigen test.
The FDA's announcement was based on a collaboration with the National Institutes of Health's Rapid Acceleration of Diagnostics program, which studied antigen tests' performance for samples that had the omicron variant.
Earlier this month, President Biden announced that his administration would purchase 500 million rapid COVID-19 tests to distribute for free to any American who wants one.
"Seeing how tough it was for some folks to get a test this weekend shows that we have more work to do. We're doing it," Biden said Monday.
Demand for tests has soared with the holiday season and the onset of omicron, making it harder to get tests.