The U.S. Food and Drug Administration (FDA) has announced that two rapid antigen at-home tests will soon be sold over the counter (OTC) on drugstore shelves. The newly authorized tests are Abbott's (ABT) BinaxNOW test and Quidel's QuickVue (QDEL).

The two tests were previously only available by prescription. However, like earlier approved at-home tests, the new tests will not be immediately available in stores. And health experts are concerned about consistently low supplies of at-home and over-the-counter COVID-19 tests.

Dr. Michael Mina, rapid testing advocate and Harvard professor of epidemiology, said he is worried about the shortage in supply versus overwhelming demand as the country looks to reopen public venues, offices and schools.

"These announcements are coming (out) but the supply is still lacking. Some of the barriers are coming down, but there are still barriers," Mina said.

Antigen vs PCR tests

It's important to note the difference between an antigen and PCR test: Antigen tests are quicker and more basic. You collect a sample with nasal swab and the test can determine if the virus is in your system. A molecular, or PCR test, is also via a nasal swab, but it requires a more intense testing process to detect the virus and whether or not there is an active infection. PCR tests are considered the gold standard for confirming a COVID-19 infection, but they usually involve a lab or point-of-care equipment to determine the results.

Mina said that antigen tests are best for surveillance, such as regularly checking if you might have the virus, and PCR tests are more necessary in clinical settings to confirm an infection.

Rapid antigen test

The cheapest at-home option is likely to come from Abbott Laboratories. Its BinaxNOW has been used by the federal government, purchased at $5 per test, to distribute to nursing homes around the country last year.

The FDA had authorized the test for use at home in connection with eMed’s digital platform for $25. Customers receive the test after eMed Apps determine they are eligible and issues a prescription. Results are available in 20 minutes.

The company expected 30 million tests to be available through eMed in the first quarter of 2021, and an additional 90 million in Q2. The test was the second at-home antigen test to receive emergency use authorization.

If an individual can’t get a test “at no charge from their state, employer or other institution, then they will need to pay out of pocket. We will provide ... guidance on how they can utilize their FSA/HSA or gain reimbursement from their health benefits organization,” an eMed spokesperson told Yahoo Finance.

While price tags for the in-store, two-test kit is not yet available, a spokesperson told Yahoo Finance it will be sold to retailers "at a per test cost in the single digits."

Quidel, on the other hand, is targeting under $30 for its two-test kit, according to CEO Doug Bryan.

Bryan told Yahoo Finance the company anticipates that it will eventually go from $15 per test to under $10 per test as it scales. The San Diego-based company is building out a new manufacturing plant in Carlsbad, Calif., that will be online in the second half of 2021 and eventually produce 600 million antigen tests per year.

The company anticipates providing millions of tests to employers as well as selling in stores starting in April. The volume of tests to employers will surpass retail stores due to the cost and manufacturing time for retail packaging.

"If we're putting these products in a two-pack format, the difficulty in packaging and pouching ... reduces that volume," Bryan said.

"We'll launch into certain geographies in stores in the month of April. It won't be widespread throughout the United States, though. We simply don't have the capacity yet to do that," he said.

Earlier over-the-counter authorizations

Australia-based Ellume’s test was the first over-the-counter test authorized and costs $30. Results are available in 15 minutes.

The company expected 100,000 tests to be available in January, by direct mail, but has not revealed where or when tests will be sold in stores.

Ellume received funding from the National Institutes of Health through the RADx Radical program, which has a $200 million budget to develop more at-home and real-time testing.

“While our initial investments in manufacturing are very large and the initial price may be higher, we are aiming to make this product as accessible as possible,” a spokesperson said of the $30 price tag.

The first at-home antigen test was authorized for Lucira last month, but it requires a prescription. Lucira’s test costs $50 and results are available in less than 30 minutes.

These two companies are much smaller and will need to invest heavily to scale. So while the FDA has already allowed their use, they are not easily available to the general public.

"I'm extremely concerned about the access and scalability," Harvard's Mina said.

At-home and over-the-counter PCR collection kits

This type of test is highly accurate. It allows for the nasal swab sample to be collected at home but must be processed by an external lab. There are several such options available through Everlywell, along with Quest Diagnostics (DGX) and through LabCorp (LH). All require a prescription from a medical professional and typically cost more than $100 out of pocket. Some are covered by insurance.

LabCorp’s Pixel was the first such test to be allowed for over-the-counter purchase this week, which means anyone can buy it without a prescription. LabCorp has not yet revealed where and when the tests will be available to purchase, nor a final cost.

“We are working with retailers and pharmacies now and hope to have something available on store shelves soon; cost is a part of those negotiations but we hope that if people meet CDC guidelines, there will be some form of reimbursement,” a spokesperson told Yahoo Finance.

All lab test results are returned within a couple of days.

More from Anjalee:

• Novavax CEO: If FDA waits for US data, 'the lag will be a couple of months' for its vaccine

• China, Russia playing 'greater-than-expected' roles in global pandemic response

• Biden COVID-19 adviser: Vaccine news is great, but we still have a ways to go

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