That’s the most recent advice from the US Food and Drug Administration (FDA), posted in December 2022, about how often asymptomatic people should take rapid antigen tests to make sure they’ve tested negative for COVID-19.

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“Not helpful, since [infected] people transmit during this time!” California Institute of Technology chemist Rustem Ismagilov, PhD, director of the Jacobs Institute for Molecular Engineering for Medicine, wrote in an email to JAMA.

Ismagilov’s research suggests the reason that it might take so long for some infected people to test positive with nasal swabs is that, at the beginning, SARS-CoV-2 viral loads are higher in the throat.

As of December, the FDA hadn’t authorized any rapid test that involves a throat swab, spokesperson James McKinny told JAMA in an email.

Yet, some studies have found that swabbing both the nose and the throat increases test sensitivity—from a little more to a lot more—than nasal swabs alone. However, other studies haven’t found an added benefit from swabbing both sites.

As Omicron began to take off a year ago, videos posted on social media suggested that throat swabs or throat and nasal swabs combined might be better at detecting the newest SARS-CoV-2 variant.

At the time, proponents had little more than anecdotal evidence to go on, but they reasoned that a sore throat was often the first symptom of an Omicron infection, so why not check there for the virus?

In response, some scientists and the FDA began posting warnings on social media against throat swabbing, noting a lack of evidence to support the value of tickling the tonsils when performing a rapid antigen test.

Although virtually all rapid antigen test manufacturers still recommend only nasal swabs, some public health authorities outside the US suggest that swabbing the throat and nose enhances the tests’ accuracy:

• Canada in the provinces of Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island, Saskatchewan

• Israel (the Israel Ministry of Health’s website refers to swabbing the oral cavity, not specifically the throat)

• The UK National Health Service offers a rapid antigen test that requires both a throat and nose swab.