The CDC Director Misrepresented the Study She Cited To Justify Her Misleading Estimate of Outdoor COVID-19 Risk

Rochelle Walensky's gloss is puzzling in light of the evidence presented in the systematic review on which she relied.


Rochelle Walensky, director of the Centers for Disease Control and Prevention (CDC), this week responded to criticism that she had grossly exaggerated the risk of outdoor COVID-19 transmission, citing a study she said supported her estimate. But Walensky mischaracterized the nature and scope of that study, and her gloss was highly misleading in light of the evidence the authors summarized.

When the CDC released new recommendations for vaccinated people last month, Walensky said "less than 10 percent of documented transmission[s], in many studies, have occurred outdoors." As critics such as New York Times columnist David Leonhardt and Reason science correspondent Ronald Bailey pointed out, that statement, which was widely echoed by the press, was true but deceptive, since it implied that outdoor transmission's share of infections is close to 10 percent—a figure that may be off by two orders of magnitude.

When Sen. Susan Collins (R–Maine) asked Walensky about her estimate during a hearing on Tuesday, Walensky said it came from a "meta-analysis" in "one of our top infectious disease journals." But the article to which she referred, which was published by The Journal of Infectious Diseases in February, describes a systematic review, which searches and summarizes the relevant scientific literature, rather than a meta-analysis, which pools data from several studies to generate an overall result. The distinction matters because "meta-analysis" implies that the "less than 10 percent" estimate was calculated based on the underlying data from multiple studies, when in fact it is a gloss that creates a misleading impression of the evidence.

Walensky also claimed that "over 19 studies were included" in the systematic review. The actual number was 12, only five of which looked at COVID-19 specifically. (Five "reported on influenza or influenza-like viruses," while two "reported on adenovirus transmission.") Of the five COVID-19 studies, according to the Journal of Infectious Diseases article, one found that outdoor settings accounted for 0.03 percent of infections; another put the share at less than 0.9 percent; and one found that "5% of work-related cases occurred outdoors."

Another COVID-19 study calculated the ratio of indoor to outdoor transmissions. It found that the "odds of transmission in closed environments was 18.7 times…greater than in open air." It also found that super-spreading, defined as transmission to three or more people, was 32.6 times more common "in closed environments" than outdoors.

The fifth study described a COVID-19 outbreak at an overnight camp in Georgia. The authors of the systematic review note that "the outbreak was clustered by cabin assignments, which suggests a high likelihood of transmission in indoor spaces during overnight cabin stays rather than during outdoor activities during the day."

None of these studies suggests that outdoor transmission accounts for anything like 10 percent of COVID-19 cases. Even the highest estimate—"5% of work-related cases"—is far lower than 10 percent, and that number is probably biased upward because of misclassification.

Leonhardt notes that "a very large share of supposed cases of outdoor transmission have occurred in a single setting: construction sites in Singapore." The likely explanation: Infections among construction workers were automatically treated as outdoor transmissions even though they may actually have happened indoors. "When academic researchers began collecting Covid data from around the world," Leonhardt writes, "many chose to define outdoors spaces very broadly. They deemed almost any setting that was a mix of outdoors and indoors to be outdoors."

That issue aside, the notion that outdoor settings account for close to 10 percent of cases is not consistent with any of the COVID-19 studies covered by the systematic review that Walensky cited. "Given that 90% of time is spent indoors in high- and middle-income countries," the authors note, "it would be expected that 90% of transmission occurs indoors, all else being equal." If outdoor transmission's share were in the neighborhood of 10 percent, in other words, the outdoor risk would be nearly as high as the indoor risk. Yet Walensky herself said there is "almost a 20-fold increased risk of transmission in the indoor setting [compared to] the outdoor setting."

To be fair, Walensky's "less than 10 percent" estimate is consistent with the language used in the abstract of the study on which she was relying. "Five identified studies found a low proportion of reported global SARS-CoV-2 infections occurred outdoors (<10%)," it says. On Tuesday, Walensky described that statement as "the top-line result." But anyone who reads the study can see that the "less than 10 percent" estimate is excessively conservative, and the abstract itself says the researchers considered five COVID-19 studies, not "over 19."

Two of the three studies that estimated the share of infections traceable to outdoor settings put that number at less than 1 percent. A more recent study that was not included in the systematic review found outdoor transmission accounted for 0.1 percent of infections in Ireland. "I'm sure it's possible for transmission to occur outdoors in the right circumstances," Aaron Richterman, an infectious disease expert at the University of Pennsylvania, told Leonhardt, "but if we had to put a number on it, I would say much less than 1 percent." There is obviously a huge difference between "less than 10 percent" and "much less than 1 percent."

Walensky's misrepresentation of the evidence matters because the general public depends on the CDC for authoritative health advice. It matters because Walensky is supposed to be a neutral expert who accurately summarizes the science that the Biden administration claims to be following. And it matters because the excessive conservatism of her estimate is reflected in the irrational caution of the CDC's COVID-19 guidelines.

If the CDC believes that outdoor transmission might be 10 or 100 times as common as the research suggests, it is easier to understand the agency's absurd, unworkable guidelines for summer camps, its recommendation that unvaccinated people routinely wear face masks in outdoor settings, and its advice that even vaccinated people should wear masks in some outdoor situations.* But the CDC should not believe that, because that is not what the evidence indicates.

"I always considered the CDC to be the gold standard," Collins said during Tuesday's hearing. "I don't anymore." Kavita Patel, the Obama administration's health policy director, expressed similar disappointment in a CNBC interview that night. "I think the CDC's credibility is eroding as quickly as our cases of coronavirus are eroding," Patel said. "That's not good news, because we do need workplace guidance; we need school guidance."

Walensky seems oblivious to the impact that careless statements and scientifically dubious advice have on the CDC's reputation. "My promise is that CDC will continue to follow the science as our guide," Walensky told senators on Tuesday. The problem is she thinks the CDC is already doing that.

*Update: Today the CDC issued revised guidelines that say fully vaccinated people do not need to wear face masks outdoors or indoors unless they are required to do so by businesses or the government.

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  1. CDC staffed by lying fascist weasels. Whodathunkit?

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    2. Three truisms:

      Democrats lie.
      Politicians lie.
      Government workers lie.

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  2. Good for Sudan Collins. Living up to the standard set by Margaret Chase Smith. Yessah!

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  3. Top. (Wo)Men.

  4. Great article, Jacob. Thank you.

  5. Listen, if we’re going to make government the most important thing in the world ever, could we at least demand that the government-appointed experts who talk out of their ass get dealt with?

    If we’re going to throw people in jail for not wearing masks, then how much more should we punish our societal expert for misleading society on critical health issues?

    That’s assuming, of course, that the whole affair is about the maximum well-being of our society, rather than just a tool for keeping the peons in their place.

    1. Like they really give two fucks about your health.

      1. Two fucks is just to get the interview. It takes five fucks to get the job.

        1. Willie Brown’s price sheet?

    2. This woman had an anxiety attack on national TV over variants, and her predecessor said that face diapers were more protective against viruses than a vaccine. I’m not sure we can expect anything more out of these people than talking out of their ass.

    3. This is one of the more frustrating part of the general status quo. Incompetents hardly ever get fired.

      1. Incompetents hardly ever get fired.

        If only there were a political candidate notorious for turnover and firing people…

        1. They would certainly trump the current crop of politicians.

        2. If only Trump had lived up to his reputation in that respect…

  6. Remember: Doom is impending!

    1. DOOOOOM!

    2. As the prophet Greta foretold, in the book of Climate Change.

  7. As a scientist she does her work as a bureaucrat. No science required, just the usual skills needed to rise to the top of a government organization – taking unearned credit, denying blame, cutting down perceived opposition, you know the rest.

    1. Fauci is a bureaucrat as well he may have been a doctor but he is now just another bureaucrat.

  8. I guess appointing Chicken Little as CDC Director wasn’t such good idea.

    1. Chicken Little identified as an expert, so there was no real choice – – – – – – –

    2. Biden’s handlers managed to find someone even worse than Redfield.

  9. I’m glad we’re finally challenging the bullshit.

    1. Only took 14 months.

  10. Well, like Fauci, she’s a propagandist first, scientist second.

    1. Propagandist by trade, bureaucrat by practice, scientist by name.

      1. Typical of Biden appointees.

  11. Thanks for linking to the article. I want to take a look at it later when I get a chance.

    Just looking at the abstract it seems all she needed to say is that we do not have consistent reliable data which is what the authors say. I see where she gets the <10% number but that seems very ambiguous.

    I don’t really follow these kinds of statements from CDC or other politicos. Media reports are even worse.

    I went to the preschool graduation (cute) at the local synagogue yesterday. They have stayed open throughout. They rely on the advice of their own medical committee. So the kiddos wear masks indoors, well some of the time, 4 year olds. I don’t think they do anything because you know how small children are.

    So the point is the CDC is not the law and is getting more attention than it deserves. Of course they are very conservative. Nobody needs to follow their advice.

    1. Well, they have finally issued some advice worth following. Good for them; hopefully this represents a death knell for this whole stupid period.

    2. So the point is the CDC is not the law and is getting more attention than it deserves. Of course they are very conservative. Nobody needs to follow their advice.

      Must be nice not to own any rental property.

      1. Those come from the state. The CDC has no ability to make laws.

  12. Yesterday, <100% of the people on the planet died from COVID related complications.

  13. Say it ain’t so sullum. You dutifully bleated the CDC party line until it became so glaringly obvious that America has been gaslighted from the beginning that you had to bail.

    You still got the orange man bad thing going for you though.

  14. “My promise is that CDC will continue to follow the science as our guide,” Walensky told senators

    “Follow the science” is rapidly joining “Have a nice day” as a banal and meaningless utterance.

    1. Hey, it’s a free country.

      1. It is?

        1. *banal and meaningless reply*

          1. Sorry I was a bit slow……

  15. I think a better question might be why did the CDC have to wait for a published paper to summarize data found in other publications?
    Does the CDC not have subscriptions to all the major (and even most of the minor) peer reviewed medical journals and aren’t there people at the CDC qualified to read, analyze and understand all the data, and make reasonable policy recommendations based on the data? Why did they have to wait for the authors of “Outdoor Transmission of SARS-CoV-2 and Other Respiratory Viruses: A Systematic Review”?

    Most (if not all) of the references in the paper are from 2020 or even earlier – why the fuck didn’t they figure this out before MAY of 2021?

    1. It’s worth noting that most places didn’t even have mask mandates until June or July, so all these studies were almost all mask-free.

  16. was true but deceptive
    …a figure that may be off by two orders of magnitude

    Right within two orders of magnitude, wrong within normal parameters.

  17. Just so we’re clear, even by Wallensky’s most fantastically mistaken claims; in the various contexts about masks, curve flattening, herd immunity, vaccines, spillover, contact tracing, simply being outside as normal leads to at least a 9-fold (if not 90-fold) reduction in transmission.

    Espeically with regard to spillover; evidence would suggest that patient zero spent considerable time in an enclosed room with an infected bat that would otherwise sleep shoulder-to-shoulder with other bats in a colony we have yet to find.

    1. WAAAAY back in April, the New England Journal of Medicine flat-out said, “we’ve known for decades that community spread is not done through incidental contact” and that not wearing a mask when you’re outdoors and just walking past someone had a miniscule chance of getting you sick. The data bore this out later on, when cases showed people, most of whom had some type of co-morbidity, who happened to be in sustained, close contact were more likely to get sick.

      I wonder how many people ended up actually getting sick and dying because the CDC and the Lying Ass Media said that people needed to stay locked up in their house, rather than going outside and getting fresh air and exercise.

      1. I wonder how many pedestrians got hit by cars after jumping into the road because they were so insistent on social distancing that they spend a split second walking by someone on the sidewalk.

        1. that they *wouldn’t* spend a split second walking by someone on the sidewalk. Sorry for the typo.

  18. All the “YOU GONNA DIE” stuff was meant to make Trump look bad and get Biden in. A competent regime would have flipped over to “You’ll be OK, thanks to us” within a month (you need a little time to dance on the grave of the old boss).

    In the 21st century, one would expect the party line to be established and disseminated much more efficiently. But our useless “elites” can’t even totalitarian correctly.

    1. I think the “YOU’RE GONNA DIE” narrative helps promote a lot of totalitarian ideas. “Emergency” spending, “emergency” restrictions, etc.

      1. Yeah, there’s tension between “we won! Aren’t we great” and “Never let a crisis go to waste”

    2. Unless they needed a bunch of fear among the electorate in order to pass multiple trillion dollar “relief” and “stimulus” packages without facing any scrutiny.

      Which they did.

      Mission accomplished. 400 billion for various forms of aid and stimulus. 3 trillion for god only knows what.

  19. Bureaucrats are stupid, we know.

  20. The CDC and Fauci (and subsequently, state and local health departments) have been lying about covid for more than a year.

    So who hasn’t Sullum written an article revealing that >99.9% of people who recovered from covid are still immune (as there are only 13 confirmed cases of reinfection), that more Americans have become immune from past covid infection than from vaccines, and that >70% of Americans are now immune.

    1. On April 5, Bridge Michigan reported that 246 fully vaccinated people in Michigan were later infected with the coronavirus, including 11 hospitalized and three who died. A spokesperson from the Michigan Department of Health and Human Services (MDHHS) was quoted by Bridge Michigan a week later that the deaths have since undergone a more “detailed review,” and all three had histories of earlier infections before vaccination. Moreover, neither COVID-19 nor any “other acute respiratory infection” was identified on the trio’s death certificates.

      World Socialist Web Site so take that with whatever grain of salt you want, but 243 is an awful big number (that’s still well within the claimed efficacy of the vaccine).

      1. There are a little over 10 million people in Michigan. The vax rate for folks over 16 is 54%

        So we’re looking at almost 5 million vaccinations. Of that, 243 is in no way a big number. It is about 5 one-thousandths of one percent.

        In no way diminishes how crappy it is to lose that particular lottery, or the psychological shock of losing a loved one who “wasn’t supposed to die” because they were vaccinated, but I’m thinking that those 3 deaths had an immune system issue. If neither infection nor vaccination conferred lasting immunity there’s no policy that was going to help.

    2. Fauci has been either lying, wrong, or incompetent about diseases since the mid-80’s

  21. I’m starting to think the CDC might be filled with incompetent idiots!

    And after they got so much respect for attacking the vaping crisis just a couple years ago. 🙁

  22. Same woman caught on tape by Mike Massie arguing when Massie points out her stand on vaccinating people who’ve already recovered from having COVID is the complete opposite of the paper she cites to justify her position. Massie point was vaccinate the most vulnerable first & get the least vulnerable last.

  23. Ms. Walensky should have resigned in disgust right after Jen Psaki threw her under the bus for promoting a bit of common sense in the Covid 19 panic fest. Instead, she smiled sweetly and conformed her later comments to the generalized idiocy being put forth by the panic pornography industry and its CEO Dr. Anthony Fauci. I felt sorry for her initially, though I was surprised by her naivete’. Eventually, however, we all came to realize she had been coopted and was forever more a creature of the swamp bureaucracy. Sad.

  24. I appreciate the look at the 10% fallacy. Even if 1% were an agreed number, the social and political science followers would wrongly cite that as a 1% chance of catching the virus outdoors. Yet the 1% is the percentage of all cases. All those cases have occured over time, not all at once. There’s never been a time when daily new cases passed 1% of the population. This rounds the risk to zero, regardless of what figures lie, or liars figure.

    I think I and others have fallen into a trap of talking about percentages regarding outdoor risk as if outdoor risk actually existed. It’s a red herring.

  25. All the “YOU GONNA DIE” stuff was meant to make Trump look bad and get Biden in. A competent regime would have flipped over to “You’ll be OK, thanks to us” within a month (you need a little time to dance on the grave of the old boss).Bolly4u

    In the 21st century, one would expect the party line to be established and disseminated much more efficiently. But our useless “elites” can’t even totalitarian correctly.

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