#: To detect omicron, take an rapid COVID-19 test right before a holiday gathering, experts say

Rapid, or antigen, tests can detect if you have a current infection, though they are considered less sensitive than PCR tests.

But the new omicron variant, which is driving the surge in cases in the U.S., has changed that thinking. This variant is more transmissible, has a shorter incubation period than other strains, is causing breakthrough infections among the vaccinated, and it’s hitting the U.S. at the start of the holiday season. 

“There have been plenty of examples where perhaps you test negative in the morning, but you could be testing positive by the afternoon or the evening,” said Rachael Piltch-Loeb, an associate research scientist at NYU School of Global Public Health and a preparedness fellow at Harvard T.H. Chan School of Public Health.

One of those examples comes from an office holiday party in Oslo, Norway, in late November. Eighty-one out of 110 people who attended the party had confirmed or probable cases of COVID-19, according to preliminary research published Dec. 16. Everyone who attended the party was fully vaccinated, primarily with the mRNA shots, though no one had received a booster. Each person had to get a negative test one to two days before the party.

“That’s really dramatic transmission,” Michael Osterholm, an epidemiologist and ​​director of the University of Minnesota’s Center for Infectious Disease Research and Policy, told SiriusXM last week. “This thing goes through red lights at 300 miles an hour.”

This is why some public-health experts are instead suggesting that it’s better to conduct rapid at-home tests within minutes of arriving at a gathering of any kind.

“I would argue that a much more reliable result, even amidst omicron, is a test taken 15 minutes before you enter into a gathering,” said Dr. Michael Mina, an epidemiologist who recently left Harvard to join eMed, which markets at-home COVID-19 tests, as chief science officer.

Mina made the remarks Tuesday during a press call. 

Not only is omicron thought to be more transmissible than other SARS-CoV-2 strains, it also is believed to have a much shorter incubation period, of two to three days, compared with four days for delta and approximately five days for the original strain of the virus. Within weeks of omicron’s detection in the U.S., it’s already the most dominant version of the virus in the U.S. 

“It replicates incredibly quickly,” Piltch-Loeb said. “That’s why we’re seeing shorter incubation periods with this variant. And that’s also why our protocol for using rapid tests should be a little bit different.”

The emergence of this particularly vexing variant heading into the second pandemic holiday season has renewed COVID-19 anxieties for some people and raised broader questions about how best to use tools like at-home tests. Though they are considered a positive addition to the pandemic toolbox, rapid at-home tests are also expensive, at least $10 per test, and not always easy to find on store shelves.

Experts say the tools that have been available all along this year—vaccination, testing, using outdoor space to gather, if possible, and masking—still work. We just have to make some tweaks, especially how we use and supply rapid at-home tests. 

Mina recommends that people perform rapid tests in their cars in the driveway when they arrive at a party or gathering and to keep the tests at room temperature, saying that cold temperatures can damage their effectiveness. 

“There’s a real need to be able to live life in the safest way possible while still having it move forward,” he said. “Rapid tests are one of the most powerful tools that have not really been utilized in a powerful way in this pandemic.” 

The White House said Tuesday it is planning to provide 500 million free rapid, at-home tests to people in the U.S., starting in January.

At the same time, the exponential growth in new COVID-19 cases over the last week has fueled demand for at-home tests, including Abbott Laboratories’
ABT,
+2.75%
BinaxNOW, iHealth Labs. Inc.’s at-home antigen test, and Quidel Corp.’s
QDEL,
-0.42%
QuickVue At-Home test. (The Food and Drug Administration said Wednesday that the BinaxNOW and QuickVue antigen tests can pick up omicron as well as other variants.)

Many pharmacy chains that carry at-home COVID-19 tests say they are seeing unprecedented demand for these products right now. Some tests are unavailable to purchase online. The stores say they can be found on shelves, though purchases are now being limited. 

As of Tuesday, CVS Health Corp.
CVS,
+0.11%
said it is limiting the purchase to six at-home tests per order. Walgreens Boots Alliance Inc.
WBA,
+0.90%
has a limit of four at-home tests per purchase, and Walmart Inc.
WMT,
+0.13%
limits orders to 8 testing kits, according to statements from each company. On Wednesday morning, several tests were out of stock online at these chains. 

People can also get in-person rapid or PCR tests at clinics and mobile testing sites; however, in regions undergoing surges, like New York City, that can require waiting sometimes hours to get a test, and results can be delayed. 

“I personally believe that we’re way beyond the days of standing in line,” Mina said. “And I’m totally disheartened to drive down Boston [Street] and see people standing in the cold in line to get a PCR test because they can’t get a rapid test anywhere.”

Read more of MarketWatch’s coverage of rapid, at-home COVID-19 tests:

‘This is a critical moment,’ Biden says, while rolling out free, at-home COVID tests as omicron spreads

Biden plans to distribute 500 million at-home COVID-19 test kits. Here are the states and cities already providing free tests.

Is it safe to travel for Christmas as omicron spreads? Here are 5 steps to stay healthy during the holidays