This recommendation from @CDCgov, coupled with the rationale given, beggars belief.

This is thinest of absence-of-evidence arguments.

Imagine what would have to be true of young adults for re-entry testing to *not* be helpful.

For starters:

1. No transmission from asymptomatic patients.

2. No transmission from mildly symptomatic patients.

3. No pre-symptomatic transmission, or >2 day turnaround on tests.

Here are the CDC guidelines: https://www.cdc.gov/coronavirus/2019-ncov/community/colleges-universities/ihe-testing.html

It's true that entry testing will not catch 100% of cases. But it's a powerful way to reduce the initial number of cases circulating in the community, and least give oneself a fighting chance in tricky environment.

It's hard for me to fathom the motivation, though the guidelines give some clues.

It sounds like there's concern about testing capacity and they're reluctant to recommend entry testing if the tests are needed for symptomatic people elsewhere.

I completely disagree with this approach. If that is the concern, the CDC needs to recommend testing and then acknowledge that in some circumstance the recommended approach may not be feasible because of overwhelming need to use those tests elsewhere.

But if you don't even recommend testing, you are not putting pressure on universities to think spend the next two months figuring out how to scale up testing capacity—something which is obviously a desperate need in most parts of the country.

There's a ton of uncertainty swirling around COVID, but one thing I am very confident of is that testing asymptomatic individuals provides an important line of defense against spread against the disease. Entry testing is powerful; I want to see frequent on-going testing as well.

Ted Bergstrom and I stressed this in a recent @Chronicle of Higher Education piece. Note also that the number of tests needed can be dramatically reduced by using batch testing.

http://ctbergstrom.com/publications/pdfs/2020CHE_full.pdf

I can't venture to guess the motives of the CDC here. Maybe it's mere incompetence rather than the ongoing slow-walk of testing. Hanlon's razor strains.

But this sure looks like the agnotology playbook: manufacturing enough doubt to justify inaction: https://ritholtz.com/2016/06/frightening-global-rise-agnotology/

It also looks a lot like the disastrous advice that John Ioannidis published last March. When the train is bearing down on you, don't run—stop and take measurements. It might on the parallel track, or even coming to a stop. A shame to waste steps without knowing they are needed!

Many colleges and universities, concerned about testing costs but under financial pressure to restart in-personal classes in the fall, will indubitably use these CDC guidelines as cover to open up while doing far too little to ensure the safety of students, faculty, and staff.