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Home / Science / Health /  As Delta variant surges, so does demand for at-home covid-19 tests

Demand for at-home Covid-19 tests has risen sharply in recent weeks as the Delta variant surges across the U.S., causing test makers to scramble to keep pace.

Abbott Laboratories said it expects supplies of its at-home test to be limited in the next few weeks as it hires workers and reboots factory lines that were slowed or idled earlier this summer. Availability on Amazon.com of Abbott’s BinaxNOW test and a similar test made by Quidel Corp. has been spotty, and an at-home test made by Ellume USA LLC was out of stock as of Wednesday. The tests, which detect fragments of viral proteins called antigens, can be found with patchy access on store shelves and websites.

An at-home molecular test made by Lucira Health Inc. is out of stock on the company’s website. A company spokesman said Lucira is boosting production.

Abbott, which has shipped tens of millions of at-home tests, scaled back production of its tests in early June and July, when demand was low, and laid off workers in Illinois and Maine.

“While there will be some supply constraints over the coming weeks as we ramp back up—we are putting resources from all over the company to help meet this unprecedented demand," an Abbott spokeswoman said in a statement. “It’s difficult to scale up on a dime, but we’re doing so again, just as we did last year."

Ellume is preparing to begin 24-hour production and working on getting a U.S. manufacturing facility up and running, said Juliet Grigg, medical adviser of the Australia-based company. A spokeswoman for Quidel said the company is working closely with retailers to keep its test stocked to meet the elevated demand.

At-home antigen tests, which are available over the counter and can give results in about 15 minutes, first appeared online and on pharmacy shelves in spring 2021. For months, some public-health experts have pushed for wider awareness and use of the tests, calling them underused tools that can help identify infectious cases quickly and thereby help prevent the spread of Covid-19.

“It’s a tool that we haven’t had, and I don’t think we’re using it to our full advantage," said Dr. Darlene Bhavnani, an infectious-disease epidemiologist at the University of Texas, Austin.

Much of the Covid-19 diagnostic testing in the U.S. has involved not antigen tests but molecular tests, which detect the virus’s genetic material and typically are processed by laboratories—a more time-consuming process. As of Aug. 19, labs in the U.S. were processing more than 900,000 molecular Covid-19 tests a day, mostly those that use a technique known as polymerase chain reaction, or PCR. That is up from about half a million a day in early July but still below the peak of around two million last fall and winter.

Antigen tests often lack a reliable mechanism for reporting results to public- health officials, meaning most such tests and results remain uncounted at a local or national level. Ellume, whose antigen test reports a user’s results, ZIP Code and date of birth to federal health authorities, has seen a jump in its use in the past month to more than 13,000 tests processed a day.

Demand for Covid-19 testing plummeted last spring and earlier this summer as vaccination efforts picked up steam, people grew weary of pandemic precautions and federal health officials said that, in the absence of symptoms, vaccinated people didn’t need to test even if they came into contact with people infected with the coronavirus. Many testing sites closed or were converted into vaccination sites.

Earlier this summer, demand for rapid testing was low even as health authorities in some areas were giving them away. But it ramped up quickly as the Delta variant started to take off.

In June, the Washtenaw County Health Department in Michigan began offering county residents free boxes of antigen tests as part of a federal research project in several communities to see whether communitywide testing could help limit spread of the virus. In the first six weeks of the project, the health department distributed roughly 2,000 test kits. In the next six weeks, starting in mid-July, they were able to distribute an additional 6,000 kits.

“It took a little time for folks to understand the value of this test and how easy it was to use," said Juan Marquez, the department’s acting medical director. “As the cases started to pick up a little bit and they saw how easy it was, we got more and more requests."

Researchers are tracking Covid-19 spread in communities with and without access to the testing program but haven’t yet published their findings. Dr. Marquez said the department planned to purchase and distribute more tests.

The surge in Covid-19 cases isn’t the only reason for the recent rise in demand for Covid-19 tests, public-health experts say. Other potential factors: students and staff heading back to classrooms; the implementation of new vaccination or test mandates by some cities, states and employers; and study data suggesting that vaccinated people can transmit the virus—and the corresponding updated federal guidance.

As a result, some states and cities across the country are once again boosting their test programs. In Mississippi, for example, health officials have added testing sites and expanded their hours of operation, state officials said during a media briefing last week. The state has ordered an additional 300,000 rapid tests.

“We have heard from some facilities regarding some difficulty with obtaining rapid tests," said Mississippi state epidemiologist Dr. Paul Byers. “We are working to be able to provide rapid tests to clinics and other facilities as we can."

Public-health experts say molecular and antigen tests are both of critical importance for finding cases of Covid-19 and stemming spread of the coronavirus—and which test or combination to use often depends on the situation.

Antigen tests are less precise than molecular tests, so they can miss cases and sometimes require follow-up testing. But their ability to give results in minutes—rather than the hours or days before the results of molecular tests typically are available—makes them crucial in some circumstances. Antigen tests work best with people who are shedding lots of virus particles and thus likely to be contagious, leading some public-health experts to call them “contagiousness tests."

Research shows that the reliability of antigen tests can be enhanced by administering them repeatedly over the course of several days. In a National Institutes of Health-funded study published recently in the Journal of Infectious Diseases, the reliability of antigen testing was comparable to that of molecular tests when the tests were administered serially at least once every three days.

Both the Abbott and Quidel at-home tests are authorized for serial screening.

Some infectious-disease epidemiologists say antigen tests might be particularly valuable for flagging Covid-19 cases caused by the Delta variant, which according to recent research causes people to become infectious sooner and shed more virus particles than other variants.

“Even if you don’t have symptoms, you’re more likely to transmit the higher your viral load is," said Dr. Bhavnani, the University of Texas epidemiologist. “We really need to be paying attention to viral loads more and more, and this raises the possibility of antigen-based tests being even more effective."

At $20 or more for a two-pack of tests, antigen testing is currently too expensive in the U.S. for most people to use regularly, public-health experts say. A handful of additional at-home antigen tests from test-makers OraSure Technologies Inc. and Access Bio Inc. recently got Food and Drug Administration authorization but aren’t yet on the market, and Becton, Dickinson & Co. said on Wednesday that it had received authorization for its at-home test.

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