New Hampshire is conducting a groundbreaking experiment in offering free at-home rapid COVID tests to all residents, and one outcome is already clear: Demand is sky-high.

Within a day of the Nov. 29 blanket offer to send eight tests via Amazon.com trucks to the door of any resident, all 800,000 had been snapped up. As the state leads the nation in per-capita cases and hospitals overflow, officials are promising another round.

Growing demand for COVID tests has made them hard to come by in Maine and elsewhere, even as cases are surging. Maine reported a record number of new infections and intensive care patients Thursday, and the state’s top public health official predicted the surge is going to get even worse in the coming days.

Widespread rapid testing, common in some other countries, is seen by experts as crucial to contain the pandemic bedeviling the U.S. and the Biden administration. The president’s spokeswoman said this week that while the administration backs free testing for anyone who wants it and 50 million free tests are going out to community sites, sending tests to all homes might be wasteful.

Gov. Chris Sununu has faced bitter opposition to vaccination campaigns and mask mandates in New Hampshire, a state of 1.4 million with a flinty libertarian streak. But the tests-for-all-takers program is a winner, he said.

“It was so successful, we’re going to do it again,” Sununu, a Republican, said in an interview. A federal program supplied the 800,000 tests from Quidel Corp., but, “if we have to pay for it ourselves, we have funds, and we’ll do it,” he said.

“The demand was so high, and I really believe it is a key aspect in pushing back on transmission of this virus.”

In recent months, rapid antigen tests have gained credibility as tools for stemming COVID’s spread – and for keeping the pandemic-era economy running by helping children stay in school, parents stay at work and families and friends gather more safely.

Alison Gage, who lives in the town of Sandwich, said the tests would make her welcome when she visits relatives in New York and New Jersey for Christmas, even though she’s coming from a hot spot. She likes the do-it-yourself aspect: “Having these free tests, I’m more likely to swab myself than have somebody swab my nose for me,” she said.

The New Hampshire program could also produce useful data on free home rapid tests just as the Biden administration is facing mounting questions about why it doesn’t just deliver them across the country. Last week, it ordered insurers to cover rapid tests, and it has committed roughly $3 billion to dramatically expand the supply of rapid tests, including millions of free kits for community sites such as clinics and health centers.

“Our approach is not to send everyone in the country a test, just to have millions of tests go unused,” White House spokesperson Jen Psaki told reporters.

Some health experts have been calling for wider distribution like New Hampshire’s – or the copious free tests given out in the U.K., Singapore and elsewhere. Fast tests let citizens know when to quarantine and help officials swiftly contain localized outbreaks.

“Increasing capacity for rapid frequent testing is something that I would hope the administration could do much better with,” said Harvard T.H. Chan School of Public Health epidemiologist Stephen Kissler.

There are few numbers to show tests’ specific impact, and some countries where they’re plentiful still see surges. But “I’m absolutely convinced that they’re helpful,” Kissler said, particularly before large gatherings, to reduce super-spreading events that are “the fuel for the fire.”

U.S. demand for rapid at-home tests skyrocketed last summer as another COVID surge began and many in-person activities resumed, leading to a months-long supply crunch and consumer complaints. Rapid tests may cost $12 apiece in U.S. pharmacies; in the U.K., residents have been able to order up to seven tests per day free.

The Biden administration has said it aims to quadruple U.S. rapid testing capacity to 200 million tests a month in December.

The U.S. Food and Drug Administration has authorized 11 nonprescription rapid antigen tests – made by companies like Abbott Laboratories, Quidel and Becton Dickinson and Co. Abbott expects its virus-testing revenue to top $3 billion for the second half of 2021, far above an earlier projection of as little as $500 million. The global market for rapid COVID-19 antigen tests is expected to expand from $5.3 billion in 2020 to $8.3 billion by 2027, according to Grand View Research Inc.

New Hampshire’s program is run under the auspices of the National Institutes of Health, part of its “Say Yes! COVID Test” initiative. In nine local programs, demand has varied, said Rachael Fleurence, who oversees the program for the agency. New Hampshire and Honolulu County, Hawaii, have been the only sellouts.

“This is the first time that the nation has home-tested at this scale,” Fleurence said. “Where a whole state is ordering home tests, that’s a new world.”

The New Hampshire tests are the first fully statewide offering her program has run.

The offering “just struck a chord,” said Patricia Tilley, the state’s director of the Division of Public Health Services. “Word of the tests spread like wildfire. We heard from lots of folks that someone in an office or on Facebook would post it, and it would just travel quickly.”

The state aims to offer as many 750,000 more tests by the end of the month, she said, and they are already arriving in Amazon warehouses.

Bethlehem education consultant Erin Talcott is among those who signed up quickly and told everyone she knew. She has already used two on her toddler daughter, Lily, to be sure her cold wasn’t COVID so she could go to daycare.

“If we could sign up again, we definitely would,” she said. “This is so much easier than getting her into her car seat and getting her to the hospital” for a test.

State officials have heard few complaints about the free tests — a striking silence in a state where some vociferously resist masking and vaccine mandates as incursions on personal freedom.

The tests “just kind of hit the right note,” Fleurence said. “Just making it really about individual choice and individual decision-making.”

State officials expect the surge to last for weeks. Sununu, asked how big a difference the tests could make as many are gathering for the holidays, said: “Huge.”

People who get tested for COVID often don’t get results back for as long as two days, he said. “That’s when the virus is most likely to spread. Well, we’re taking that 24 to 48 hours and making it an hour. You have a runny nose? You can take a test now.”