How is the CDC so wrong?!

So I listened to a great interview today between Ezra Klein and Michael Lewis.  I mean, talk about podcast nirvana for me.  I love listening to both of these guys so much.  Anyway, it was largely about Lewis’ latest book (high in my personal queue) about the pandemic in which the CDC is the primary villain.  My favorite part was their discussion of public health bureaucracies and how they seem to be way tilted towards errors of omission (which can be really bad in a pandemic) instead of errors of commission and thus risk averse to a very flawed extreme.  

I finished listening to the podcast and read my daily Leonhardt (and, really, if you are not subscribed, for this free newsletter, you really should be) and it was about an absolutely embarrassingly wrong-headed estimate of outdoor transmission from the CDC.  If you follow the science on this at all, you know that a “up to 10%” outdoor transmission rate is simply fantastical and it genuinely undermines CDC credibility to put out public guidance like this.  This money quote from Leonhardt captures it perfectly:

Saying that less than 10 percent of Covid transmission occurs outdoors is akin to saying that sharks attack fewer than 20,000 swimmers a year. (The actual worldwide number is around 150.) It’s both true and deceiving.

Plenty of good stuff from Leonhardt on how the CDC got to such a flawed estimate which actually mirrors my experience of digging into indoor vs outdoor numbers.  At some point classifying something as “outdoor” just because it has some outdoor component is not a “conservative” approach, but rather a wrong-headed and misleading approach.  

This isn’t just a gotcha math issue. It is an example of how the C.D.C. is struggling to communicate effectively, and leaving many people confused about what’s truly risky. C.D.C. officials have placed such a high priority on caution that many Americans are bewildered by the agency’s long list of recommendations. Zeynep Tufekci of the University of North Carolina, writing in The Atlantic, called those recommendations “simultaneously too timid and too complicated.”

They continue to treat outdoor transmission as a major risk. The C.D.C. says that unvaccinated people should wear masks in most outdoor settings and vaccinated people should wear them at “large public venues”; summer camps should require children to wear masks virtually “at all times.”

These recommendations would be more grounded in science if anywhere close to 10 percent of Covid transmission were occurring outdoors. But it is not. There is not a single documented Covid infection anywhere in the world from casual outdoor interactions, such as walking past someone on a street or eating at a nearby table…

I asked the C.D.C. how it could justify the 10 percent benchmark, and an official there sent this statement:

There are limited data on outdoor transmission. The data we do have supports the hypothesis that the risk of outdoor transmission is low. 10 percent is a conservative estimate from a recent systematic review of peer-reviewed papers. CDC cannot provide the specific risk level for every activity in every community and errs on the side of protection when it comes to recommending steps to protect health. It is important for people and communities to consider their own situations and risks and to take appropriate steps to protect their health.

Erring on the side of protection — by exaggerating the risks of outdoor transmission — may seem to have few downsides. But it has contributed to widespread public confusion about what really matters. Some Americans are ignoring the C.D.C.’s elaborate guidelines and ditching their masks, even indoors, while others continue to harass people who walk around outdoors without a mask.

All the while, the scientific evidence points to a conclusion that is much simpler than the C.D.C.’s message: Masks make a huge difference indoors and rarely matter outdoors.

The health authorities in Britain, notably, seem to have figured this out. They have been more aggressive about restricting indoor behavior, locking down many businesses again late last year and requiring masks indoors even as most of the country is vaccinated. Outdoors, however, masks remain rare.

Anyway, if a public health agency is going to err, yes, it should err on the side of caution.  But, it should actually aim to err as little as possible, rather than putting out completely absurd numbers, like “up to 10% outdoors.”  And, they case of the UK (and others) shows that you absolutely can get this right.  

You’d kind of hope that Biden being president would solve a lot of problems at the CDC (and FDA), but they are clearly pretty deeply engrained.  

About Steve Greene
Professor of Political Science at NC State

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