The White House allocated an additional $1 billion to buy millions of rapid at-home COVID-19 tests earlier this week.

Why it matters: Rapid tests can quickly determine whether you're infected with COVID-19 and at risk of spreading it to others, but lack of funding — and slow approval — has led to a dire shortage.

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Driving the news: White House COVID-19 response coordinator Jeffrey Zients told reporters on Wednesday that the new funding — as well as an additional $2 billion allocated in September — will quadruple the number of available tests over the next few months.

• Earlier in the week the FDA also authorized Flowflex, a rapid at-home test made by ACON Laboratories that the White House expects will retail at about $10 per test, making it cheaper than other available diagnostics.
• "We'll have available supply of 200 million rapid at-home tests per month, starting in December," he said.

How it works: Rapid antigen tests — which can deliver results in as little as 15 minutes — are particularly useful for the current moment.

• As millions of Americans return to school and the workplace, rapid tests can let them quickly determine their COVID-19 status if they've been exposed to the virus or they begin to show symptoms.
• My thought bubble: My wife and I used one of our last remaining rapid tests this past weekend on my as-yet-unvaccinated 4-year-old so he could attend a bar mitzvah with us. (He was negative, which was fortunate because the party had both pizza and foosball.)

The catch: In part because of that utility, however, rapid tests have become increasingly difficult to find.

• "Employer demand has gone crazy," Doug Bryant, CEO of testing company Quidel, told Reuters. "We won't be able to meet all the requests that we're having."
• Even if the U.S. can get to 200 million rapid tests per month, it will mean less than one test per person at a time when both COVID-19 and traditional winter infections like the flu will be active.

What's next: This week, the FDA also authorized a new lab-based test from PerkinElmer that can detect COVID-19 as well as influenza and respiratory syncytial virus — a capability that should be especially useful this winter./   Axios