Shortly after it was discovered in December 2021 that commonly used at-home antigen COVID-19 tests may not always accurately detect the Omicron variant, the U.S. Food and Drug Administration issued emergency-use authorizations for two at-home tests that experts said were better designed to detect the highly contagious coronavirus variant.

The new tests—Roche’s COVID-19 At-Home Test, and Siemens Healthineers’ Clinitest—are set to hit the shelves in the coming weeks.

A spokesperson for Roche told the Washington Post that consumers will be able to purchase the new tests beginning in late January, while a Siemens spokesperson said it was too early to say when tests will arrive in stores, but added production was ramping up.

In a statement to Fortune, Roche spokesperson Michelle A. Johnson said it is the company's intent "to bring tens of millions of tests per month into the market with an initial focus on community-based testing at large scale and efficiency." The company also plans to "work with retailers and pharmacies in late March to provide broad access to this test across the United States." Siemens told Fortune it was “making millions of rapid COVID-19 antigen tests available to the American people,” but did not specify a timeline.

At-home rapid antigen tests were never expected to be completely reliable, especially compared to the PCR tests that are performed in a lab or clinic, according to health experts.

“When you’re dealing with an antigen test, everyone knows from the beginning that it is not, by the nature of the technical aspect of the test, as sensitive as a PCR—so it isn’t 100% sensitive,” Dr. Anthony Fauci said during a recent White House briefing.

Rapid tests work by detecting antigens, which are proteins that live on the surface of the virus. The sensitivity of the antigen tests vary depending on the amount of virus within one person. This means a person needs to produce a higher number of antigens to produce a positive result in a rapid test. But someone can be positive for COVID and still test negative on an at-home test because the person’s viral load is not high enough to be detected.

Most antigen tests have a sensitivity rate that ranges from 50% to 90%, meaning they produce a high rate of false negatives. PCR tests, by contrast, produce about a 98% sensitivity rate, which means they are more accurate at detecting the virus and rarely produce false negatives.

The two new antigen tests are significant because they “perform really well” at detecting Omicron when compared to the existing antigen tests available in stores, said Wilbur Lam, the physician who runs the lab enlisted by the National Institutes of Health to evaluate the effectiveness of rapid tests on the market, told the Washington Post.

The nationwide Omicron peak is likely weeks away, but consumer demand for the at-home, rapid antigen tests has reached its highest levels since the pandemic began.