Here’s How and When to Test for Covid-19

With Omicron Cases Surging, Here’s How and When to Test for Covid-19

Holiday gatherings, travel and a shortage of tests in some places make it essential to have smart strategies for testing now

Testing is recommended for anyone who plans to gather with friends or family in a setting that would be indoors and maskless .

By Betsy Morris, WSJ

Updated Dec. 21, 2021 3:43 pm ET

The fast-spreading Omicron variant is fueling a surge of Covid-19 cases in many parts of the U.S. right as millions of Americans are planning holiday gatherings and travel. The rise is creating a rush for tests, and a host of questions about when and how to test—especially with at-home kits and appointments difficult to come by in hard-hit areas.

We asked doctors about the best strategies for testing. Here’s what they said.

In what circumstances do I need to test?

There are three main scenarios that call for Covid-19 testing during the holidays, doctors say.

Test when you have symptoms including sore throat, cough, runny nose or fever, doctors say. The result will help determine whether you need to isolate for 10 days and whether you need to call a doctor to seek treatment. Antiviral treatments such as monoclonal antibodies are already available. Other treatments developed by Ridgeback Biotherapeutics and Merck & Co., as well as from Pfizer Inc., could be authorized for use in the U.S. soon for certain adults.

Test when you know you have been exposed to Covid-19, whether you learned via a contact-tracing notification or discovered that someone you have been close to tested positive. Rapid antigen tests aren’t likely to detect the virus early, but they are considered a good gauge of whether you have become infectious. If you have symptoms already, test right away. If the test is negative and you still have symptoms a few days later, follow up with another test.

Rapid home Covid-19 tests promise convenience and speed, but a test’s accuracy depends on how and when you take it. WSJ’s Daniela Hernandez explains everything you need to know about at-home testing and how to get accurate results. Illustration: David Fang and Jacob Reynolds

If you don’t have symptoms after the exposure, doctors recommend waiting about three to five days and then doing a rapid test. If you are infected, your viral load likely will have increased enough for the test to detect it, they say. In the meantime, take precautions such as wearing a mask around others even if you are vaccinated.

Test to screen yourself before getting together with friends or family in a setting, say, indoors and maskless, in which you are at higher risk of transmitting the virus. That is true especially if the event includes people who are elderly, immunocompromised, have underlying health conditions or aren’t vaccinated. “As a rule, plan your precautions around the most vulnerable people in the group,” says Alyssa Bilinski, an assistant professor of health policy at the Brown University School of Public Health.

When is the best time to test before I see family and friends?

Test yourself as close to the start of the event as possible.

If you are incubating the virus, you can become contagious at any time. The rapid test does the best job of quickly letting you know whether you are contagious the moment you test yourself, doctors say.

If you are going to a party, “the best situation is to show up at a friend’s house and they are testing” at the entrance, says Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security. If the test is positive, leave and isolate for 10 days.

How do I decide whether to do a PCR test or a rapid test?

Your first pass should be a rapid antigen test, many doctors say, because it can help provide the fastest answer to the most important questions: Am I contagious and am I putting others at risk?

Rapid antigen tests—which give results in about 15 minutes—are a good gauge of infectiousness.

However, rapid tests aren’t as sensitive as PCR tests. The PCR test is better at detecting whether you are incubating Covid-19. PCR tests, though, must be analyzed in a lab and it can take days to get the results.

A PCR test is also helpful if you have any doubt about the results of a rapid test, doctors say, such as when a rapid test says you are negative but you are still sick. If you need the test to make a decision about a coming trip or gathering, “make sure you’re likely to get the test results back before you take the risk,” Dr. Bilinski says. Take the PCR test as close in time to the event as you can get it, and be cautious not to get exposed after you are swabbed, she says.

What if test kits are scarce and appointments are hard to come by? Which situations should I give priority for testing?

If you must ration your tests, give priority to those most at risk within your household, doctors say. Test the people who are vulnerable and might need treatment first, says Dr. Bilinski. Then test to get the information you would need to change your behavior, such as skipping a family dinner, if you will be with people who are vulnerable.

Should I test if I am traveling?

If you plan to travel, the Centers for Disease Control and Prevention recommends you test one to three days before and again after your travel if you aren’t vaccinated. All travelers should test themselves if they develop symptoms, the CDC says.

—Brianna Abbott contributed to this article.