The latest Covid-19 wave during the busy holiday travel season caught the U.S. flat-footed when it came to one key tool in its pandemic-fighting arsenal: at-home rapid tests.

“In the United States, we haven’t had federal guidance on how to make testing a regular part of your daily life or your daily week,” said Lindsey Dawson, a policy analyst at the Kaiser Family Foundation, in an interview with CNBC.

“A comparison is the U.K., where it’s recommended people over 11 test twice a week. And in the U.S., if everybody over 11 tested twice a week, we would need 2.3 billion tests per month, and we’re not there.”

The White House has made it clear that the tests — sold over-the-counter at drugstores — are critical to keeping the economy running during the current surge of the highly contagious omicron variant and any future variants.

Demand for at-home tests has soared as infection and hospitalization rates soared to unforeseen levels in early 2022, leading to supply constraints and accusations of price gouging.

The fight against Covid-19 appears far from over, and those at-home rapid tests look poised to play a crucial role in federal and state efforts to mitigate another tough pandemic-era winter.

The U.S. vaccination rate has stalled, leaving pockets of Americans vulnerable to severe disease. Experts also point out that kids under 5 years of age still don’t have access to an approved vaccine. 

Even vaccinated Americans are testing positive for Covid-19, and researchers are trying to understand what that means for how well the variants spread.

“What we’re seeing is our vaccines are not transmission-blocking,” said Dr. Albert Ko, the Raj and Indra Nooyi professor of public health at the Yale School of Public Health, in an interview with CNBC. “They reduce the probability that someone who’s vaccinated, who’s infected can transmit the virus to people in their households and their community.”

Federal regulators at the Food and Drug Administration have been criticized for not authorizing at-home Covid tests quickly enough to match demand. Meanwhile, the U.S. Centers for Disease Control and Prevention’s evolving testing guidance for the vaccinated also has confused test manufacturers, according to the Kaiser Family Foundation.

Watch the video above to find out how the U.S. fell behind on its at-home Covid testing strategy, and what the Biden administration is doing to fix it.