Thread by @DrTomFrieden

Some have criticized CDC’s guidance on isolation for people who test positive for Covid. I believe it’s basically correct, though they could roll it out better. 1/thread

Last night I explained what the new guidance means for you if you get Covid. Now I’m going to tackle why the guidance makes sense from a public health perspective. 2/

https://twitter.com/DrTomFrieden/status/1478935158166364168

Isolation prevents people with Covid from spreading the infection, but it has negative effects, not only on the physical and mental health of the person isolated, but also on their family and their community's ability to continue important activities. 3/

It has become quite clear that Omicron is far less severe than prior variants, and that has big implications. We don't tell people who have the flu to isolate for 10 days, or to get a test before going out. 4/

https://twitter.com/DrTomFrieden/status/1478935166940811269

So, shortening isolation for Covid to five days when possible makes sense. 5/

With the updates to the guidance, CDC has addressed the single most important issue—that people who have vulnerable contacts (including anyone who is immunosuppressed, frail elderly, or living in a nursing home or correctional facility) SHOULD stay isolated for 10 days. 6/

CDC’s testing recommendation is perhaps the biggest topic of controversy. Before going into the details, it’s worth putting this into context. 7/

We’re probably diagnosing only at most one of three new infections and there’s little or no isolation of the undiagnosed. Even among those diagnosed, evidence suggests that only about a third are isolating. CDC’s guidelines affect a fraction of 10% of infections. 8/

Isolating if you have Covid is important to protect people around you. We each have a responsibility to do our part, and the government must make it easier with policies such as guaranteed paid sick leave. 9/

The question of whether to test at the end of day five for people in isolation addresses a tiny proportion of transmission risk. 10/

Because a significant proportion of antigen tests return a false negative result, some people who test negative on day five may incorrectly assume they can stop masking. So it’s possible that recommending tests during isolation could result in MORE, not less, spread of Covid. 11/

How about those who test positive at five days? They should isolate longer. But if they never tested and followed guidance, they would have been masking anyway, with their most infectious period long over. 12/

So how many infections would be prevented by recommending testing for everyone on day five? Not many. More than those caused by people who test false negative and stop masking? Maybe not. 13/

Since those with vulnerable contacts should isolate for 10 days in any case, the primary objective of CDC’s guidance—preventing severe Covid—is achieved whether or not tests are done on day five. After day 10, transmission is rare so tests aren't necessary then either. 14/

Now, on an individual basis you might decide that you don’t want to spread Covid to anyone else, that you’d like to test on day five and if you’re positive you’re going to isolate for longer. That’s reasonable. 15/

Often, guidance for the general public and guidance for individuals is different. What makes sense to keep the whole population safest and healthiest may be different than guidance given to individuals in different circumstances or with particular concerns. 16/

That’s why, odd as it sounds, the CDC recommendation that if you want to test you can test actually makes sense. 17/

That raises a much more important and broader question: Who should get tested and when. And actually, for diagnosis of Covid, the CDC has a great website for that (see the “Get Started” box). bit.ly/3qXlOyI 18/

For those who wish to test before leaving isolation after five days, current CDC guidance breaks down the issues with using tests to assess infectiousness, and recommends actions based on whether you get a negative or positive result. 19/

Now, if CDC explains that clearly to the public, we will all be better off. 20/

There’s a right way to do public health messaging. Guidance should be technically sound, clear, simple, and practical. It should also be communicated well, ideally with media briefings that also feature subject matter experts to explain the reasoning and science. 21/

It’s likely that variants will continue to emerge. The virus is adapting. We must adapt too, and get comfortable with guidance changing as the situation changes and we learn more. 22/

CDC literally wrote the book on how to communicate in a health emergency: Be first, be right, be credible, be empathetic and give people practical, proven things to do to protect themselves, their families and their communities. 23/end