CDC Director Rochelle Walensky testifies during a Senate committee hearing.
The US Centers for Disease Control and Prevention offered differing opinions on the use of at- home rapid tests on Wednesday, as the agency continued to defend its controversial recommendation that people with COVID-19 can leave isolation early without testing.
The CDC updated its guidance last week. If the symptoms of the person have cleared and they wear a mask for five days, the isolation period will be shortened from 10 days to five. The agency didn't want people to end their isolation early if they get a negative result from a test, but they did want them to get tested after five days.
The omission was criticized by experts who argue that testing is important to shortening isolation periods. Harvard epidemiologist and rapid-test advocate Dr. Michael Mina called the move "reckless" and "bullshit."
It was a good test.
The CDC has continued to argue that the decision is backed by science, and that the majority of transmission occurs in the one-to-two days before symptoms develop. Critics pointed out that the infectiousness data is mostly from previous coronaviruses, not the current omicron variant. A lot of people will still be infectious after that window, even though the majority of transmission may occur early on.
The CDC agrees. The agency posted a defense of its position on its website. 31 percent of people remain infectious after 5 days after a positive test, according to a study from the United Kingdom. The CDC recommends that people wear a mask for five days after leaving isolation.
Advertisement
The CDC doesn't recommend testing at five days to end isolation periods safely because rapid tests aren't designed to indicate levels of infectiousness. Rochelle Walensky, director of the CDC, argued in a White House briefing that they are not quantitative tests. "They are qualitative tests to diagnose." She said that the tests are for qualitative purposes, not quantitative, meaning we can't tell how transmissible a positive or negative test is.
In an interview with CNN last week, Walensky elaborated further.
If you got a rapid test at five days and it was negative, we weren't sure if you were still transmissible. We didn't want to leave a false sense of security. We wanted you to wear the mask. We know the maximum amount of transmission was behind you if it was positive.
There is confusion and shortages.
Critics have pointed out that that assessment is not accurate. The amount of virus particles in your airway is a good indicator of how infectious you are, and the at- home tests can detect some of the remnants of the SARS-CoV-2 virus.
Critics began circulating an article co-written by Walensky in the journal Health Affairs. Walensky and her co-author wrote about it.
The more virus in the airway, the better the result. There is a high degree of overlap between the period of maximal infectiousness and the period during which the test is most likely to produce positive results.
The CDC in its online defense Tuesday included a section titled "Why does CDC not require a test at the end of isolation?" If a person has access to a test and wants to take it, they can do so around day five. If your test result is positive, you should remain isolated until day 10 because a positive test likely means a person has residual transmissible virus and can potentially transmit it to others.
