The Biden administration began allowing Americans who had ordered free coronaviruses tests this winter to request a second round of tests through the same U.S. Postal Service program that President Biden unveiled in January.

The program had a crush of interest when it was launched in January. The Omicron variant caused case rates to go up so much that tens of millions of households had to take free tests.

White House officials and public health experts say it will require a lot of effort to sustain interest in testing and ensure that manufacturers keep producing tests.

People were able to sell hot cakes over Omicron. When the libraries can give them away, the government needs to make sure that the manufacturers don't pull out like they did before Delta.

The supply of rapid at- home tests has increased. Mara Aspinall, an expert in biomedical diagnostics at Arizona State University who is also on the board of the company that makes rapid Covid tests, said that federally authorized manufacturers had the ability to make an estimated 535 million tests last month.

It is now easier to find tests at community sites. The majority of American households ordered free tests from the Postal Service website over the last seven weeks. More than 70 million tests have been delivered to 70 million households, with more than 5,000 Postal Service employees packing and shipping them.

Federal funding for at- home tests is ending, meaning that lawmakers will have to commit more money to prepare for an outbreak. The administration requested $22.50 billion from Congress for its new coronaviruses response strategy.

Testing doesn't just happen on its own. When testing demand goes down, industry reduces its output, according to Dr. Inglesby. We had a few weeks to scale manufacturing again. Without industry being prepared, that is not possible.

White House officials said that the Biden administration is still trying to get enough tests to fulfill Mr. Biden's pledge to purchase a billion of them for free distribution. Dr. Inglesby said that the federal government has begun adding tests.

The administration recently sent test manufacturers a request for information, asking what it will take for them to sustain manufacturing during a quieter phase of the Pandemic.

Inglesby said that they are committed to supporting the testing infrastructure in a way that does not let it lapse or diminish in times of quiet.

The White House was criticized by public health experts and lawmakers for not buying more at- home tests sooner, which they said could have helped meet demand when the Omicron variant arrived late last year.

Long lines formed when grocery and pharmacy shelves were emptied of tests.

Residents waited in lines to be tested in Washington in December, as  the Omicron variant surged. But cases have plummeted since then.
ImageResidents waited in lines to be tested in Washington in December, as  the Omicron variant surged. But cases have plummeted since then.
Residents waited in lines to be tested in Washington in December, as the Omicron variant surged. But cases have plummeted since then.Credit...Kenny Holston for The New York Times

The Biden administration has purchased hundreds of millions of them from a group of large manufacturers.

Some Americans received tests within days of the Postal Service website going live, but many got them weeks after placing orders. Dr. Inglesby said that the timing was the result of manufacturers having to scale up to deliver the tests.

He said that the next set of tests should be available in a few days.

Public health experts said the tests had important purposes. The mail program has helped shift the perception of rapid tests from a scarce luxury to a normal, accessible resource, according to a policy analyst at the Kaiser Family Foundation.

Making someone familiar isn't so intimidating. I can have them at home. I can use them for myself. She said that she could use them on her child and move about the world in a way that felt more secure.

The Centers for Disease Control and Prevention still recommends using at- home tests after being exposed to the virus, when experiencing Covid symptoms, or before indoor gatherings with vulnerable people.

The Biden administration will rely on testing, such as the "test to treat" initiative, which allows Americans to get tested at pharmacy, community health centers and long-term care facilities.

Some public health experts warn that people might take more risks if the C.D.C. relaxes mask recommendations for much of the country.

The youngest children are not eligible for vaccine because they have immune deficiencies.

A stay-at- home mother in Jupiter, Fla., Christina Rondinone, has kept a small amount of tests from a nearby pharmacy and the Postal Service program. She plans to order more tests from the government before she can visit her father, who is at risk of Covid if he doesn't get his lung and kidney disease under control. Ms. Rondinone said she would like to use the tests after attending crowded indoor events without a mask.

Ms. Aspinall said rapid tests were used seven times more often than P.C.R. tests. She warned that if there was not enough demand in the coming weeks and months, there would be fewer of them.

She said that companies would have to commit substantial manpower to the effort to sustain production levels, coming off a period when they worked to meet demand.

The Biden administration on Tuesday formally began allowing Americans who received a first batch of four at-home coronavirus tests this winter to order a second round.
ImageThe Biden administration on Tuesday formally began allowing Americans who received a first batch of four at-home coronavirus tests this winter to order a second round.
The Biden administration on Tuesday formally began allowing Americans who received a first batch of four at-home coronavirus tests this winter to order a second round.Credit...Doug Mills/The New York Times

She said that companies are more aggressive in managing their supply chain.

Private health insurers are now required to cover the costs of at- home tests for their members. Mark McClellan, a Duke University health policy professor who has studied the reimbursement program, said it showed signs of promise, but that it is unclear how long the program will last.

The high demand for Covid tests in recent months encouraged manufacturers and policymakers to see that there is a real utility to having these at- home tests.

She wants to see more tests so that people can be tested for the flu.