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Healthy Precaution, Not Scientific Caution

Two hundred thirty-nine scientists have signed an open letter to the World Health Organization, calling on the organization to recognize that aerosolized transmission of the virus that causes COVID-19 is a major vector of infection, along with large respiratory droplets and touching surfaces where the virus is active.

To which you might reply as I did, six months into the pandemic: You mean they haven’t already?

The excellent New York Times science reporter Apoorva Mandavilli has the best story on the controversy. She interviewed nearly 20 scientists — “including a dozen W.H.O. consultants and several members of the committee that crafted the W.H.O. guidance” — as well as reviewed internal W.H.O. emails. Just about everything Mandavilli hears shows an organization that is too scientific to be effective:

The W.H.O. infection prevention and control committee in particular, experts said, is bound by a rigid and overly medicalized view of scientific evidence, is slow and risk-averse in updating its guidance and allows a few conservative voices to shout down dissent.

“They’ll die defending their view,” said one longstanding W.H.O. consultant, who did not wish to be identified because of her continuing work for the organization. Even its staunchest supporters said the committee should diversify its expertise and relax its criteria for proof, especially in a fast-moving outbreak.

Of course, W.H.O. was also slow to endorse face coverings compared with many national public health officials and political leaders, and still insists that asymptomatic transmission is rare, which many other experts dispute. Indeed, Mandavilli reports some experts “criticized the W.H.O.’s messaging throughout the pandemic, saying the staff seems to prize scientific perspective over clarity”:

“What you say is designed to help people understand the nature of a public health problem,” said Dr. William Aldis, a longtime W.H.O. collaborator based in Thailand. “That’s different than just scientifically describing a disease or a virus.”

The W.H.O. tends to describe “an absence of evidence as evidence of absence,” Dr. Aldis added. In April, for example, the W.H.O. said, “There is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection.”

The statement was intended to indicate uncertainty, but the phrasing stoked unease among the public and earned rebukes from several experts and journalists. The W.H.O. later walked back its comments.

To me, the most interesting part of Mandavilli’s piece is hearing from many experts that W.H.O. should adopt a “precautionary principle” or a “needs and values” approach to its recommendations. In other words, these experts believe that “even without definitive evidence, the agency should assume the worst of the virus, apply common sense and recommend the best protection possible.”

“There is no incontrovertible proof that SARS-CoV-2 travels or is transmitted significantly by aerosols, but there is absolutely no evidence that it’s not,” said Dr. Trish Greenhalgh, a primary care doctor at the University of Oxford in Britain.

“So at the moment we have to make a decision in the face of uncertainty, and my goodness, it’s going to be a disastrous decision if we get it wrong,” she said. “So why not just mask up for a few weeks, just in case?”

The precautionary principle gets a bad rap — rightly so, in many cases, when it’s wielded as a pretext for never doing anything, or (on the other hand) pushing for wholesale and far-fetched structural changes in world governance and economic arrangements that themselves would be massive experiments, all in order to stop a trend that more judicious interventions might address.

Here, however, 239 scientists are recommending precaution instead of caution: precaution as a paradigm of active intervention to prevent potential harm, which also takes into account the rich and long-standing literature about the aerosolization of viruses (as opposed to this particular virus) through coughing and talking.

It’s very important for science to be rigorous, especially when the public is being overwhelmed with hundreds of papers making claims.

It’s also important to understand when your science-based organization has audiences outside of science whose needs and values require direction grounded in something less than perfectly buttoned up science, whatever that means.

In this case, the organization charged with safeguarding global public health doesn’t understand what the public needs to hear about global public health. What we should do to protect ourselves, rather than what the organization needs to say to protect itself scientifically.

Not surprisingly, Science magazine reports that messaging from the C.D.C., W.H.O. and other public health bodies about a potential vaccine for the COVID-19 virus (“authoritative and fact-filled) is already getting lapped by anti-vaccine campaigns on social media, driving down public receptivity to getting such a vaccine. Why?

Accuracy and authority are at a disadvantage in a media environment that favors speed, emotion, and memorable stories, says Peter Sheridan Dodds, a complex systems scientist at the University of Vermont who studies how ideas move through social media. Antivaccine activists have used those factors to attract followers, Dodds says. “In the end, it’s story wars.”

A better way to phrase that last judgement: Appeal to everyone’s needs and values.