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Story Publication logo October 16, 2020

Act Now, Wait for Perfect Evidence Later, Says ‘High Priestess’ of U.K. COVID-19 Masking Campaign

Volunteers from Indonesia's Red Cross prepare to spray disinfectant at a school closed amid the spread of coronavirus (COVID-19) in Jakarta. Image by REUTERS/Willy Kurniawan. Indonesia, 2020.

Veteran public health journalists from Science magazine explore what science knows—and is learning...

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“As scientists, our goal must be to cut through the rubbish,” says Trisha Greenhalgh of the University of Oxford. Image by Katty Huertas. United States, 2020.
“As scientists, our goal must be to cut through the rubbish,” says Trisha Greenhalgh of the University of Oxford. Image by Katty Huertas. United States, 2020.

In May, when several prominent U.K. scientists pushed back against a Royal Society report recommending face masks to help control the spread of COVID-19, Trisha Greenhalgh was furious. The scientists argued there was insufficient support in the scientific literature for the efficacy of masks, and the U.K. government, following their lead, declined to mandate masks for the general public.

"The search for perfect evidence may be the enemy of good policy," Greenhalgh, a physician and expert in health care delivery at the University of Oxford, fumed in the Boston Review. "As with parachutes for jumping out of airplanes, it is time to act without waiting for randomized controlled trial evidence."

Greenhalgh is a firm believer in evidence-based medicine. She wrote a best-selling book on the topic, and her research has earned some of her nation's highest honors. But in recent years, she has grown critical of what she believes is the privileging of randomized controlled studies over clinical experience and close observation. COVID-19, she argues, has revealed the limits of evidence-based medicine—masks being a potent case in point.

"The real tension in public health is, in the absence of strong evidence, whether it's appropriate to take action," says Tom Inglesby, director of Johns Hopkins University's Center for Health Security. "And a large-scale intervention like masks is extremely difficult to study." Yet the limited evidence available suggested masks could reduce the amount of virus transmitted from one person to another by more than 90%. And that, Greenhalgh insists, should have been enough to motivate an inexpensive and largely risk-free public health intervention. "Hundreds of thousands of lives were lost before many governments introduced mandatory masking," she says.

Even more lives might have been lost if not for Greenhalgh's tireless promotion of masks, which ultimately helped win over policymakers, says Chas Bountra, a professor of translational medicine and pro vice-chancellor of innovation at Oxford. She faced powerful opposition, he says. "Not every scientist would have had the courage."

Greenhalgh says she was born with an insatiable appetite for academic challenges—and a distaste for following the rules. "I nearly got kicked out of secondary school for stealing a dog and bringing him to class," she says.

Warned by a teacher that the University of Cambridge did not admit outspoken young women of "her sort," she applied nonetheless and was granted an interview. "I didn't have the proper clothes, so I made myself a suit," she recalls. Her interlocutor, Tim Hunt, a biochemist who would go on to win the Nobel Prize in Physiology or Medicine (and in 2015 became notorious for disparaging comments he made about women in science), didn't seem to notice. "He kept his head down and asked me seven questions," she says. When he told Greenhalgh she'd gotten every answer wrong, she asked him to explain, and together they reviewed the problems one by one, until she fully understood her errors. "I got my place at Cambridge because research isn't knowing the right answers before you start," she says. "It's about how you ask the questions and how systematically you go about finding the answers."

After studying social and political science at Cambridge, Greenhalgh qualified in medicine at Oxford and then embarked on a career in primary care, with a research focus in endocrinology and a passion for teaching. In 1999, noting that disadvantaged students could not afford to attend her course in international primary health care, she designed—and, for 10 years, ran—the United Kingdom's first fully online master's degree program, attended by hundreds of doctors and nurses from all over the world. "I was humbled by their passion to improve quality of care in what are often staggeringly difficult circumstances," she says.

Greenhalgh has no fear of challenging conventional wisdom. For example, in a 2014 paper that became one of the most read and shared in the history of The BMJ medical journal, she posed a hypothetical case of a 74-year-old woman prescribed a high dose of statins to lower her cholesterol, who then suffers muscle pains—a common side effect of statins—that interfere with her hobbies and ability to exercise. Greenhalgh's point was that the prescribing physician had followed protocol but had not accounted for how the patient lived her life. Such scenarios, Greenhalgh wrote, offer "a good example of the evidence-based tail wagging the clinical dog."

"She refutes any mechanical form of reasoning, be it an automatic use of guidelines or a specific research design, as unscholarly," says philosopher Eivind Engebretsen of the University of Oslo, who has collaborated with Greenhalgh for several years. "And she categorically opposes what she calls the most overused and underanalyzed statement in the academic vocabulary: that 'more research is needed.' What we need, she says, is more thinking."

As the mask debate was raging late this spring, Greenhalgh joined data scientist Jeremy Howard at the University of San Francisco to launch a website aimed at turning the tide of public opinion around the world ( Their accompanying blog got millions of views and was translated into 21 languages. "Jeremy came up with the slogan 'It's a piece of cloth, not a land mine,' which drew attention to the quite absurd framing that some anti-maskers had cooked up," Greenhalgh says. After that, the media—and policymakers—came calling.

In one TV appearance, a politician insisted masks were unnecessary because the best barrier to COVID-19 was a front door. Greenhalgh agreed that was true, but added that if people don't want to be on lockdown forever, "I suggest we take that front door, turn it on its side, shrink it down to the size of your hand, and make it out of a double layer of cloth."

Greenhalgh, whom one critic dubbed "the high priestess" of England's masking campaign, joined a World Health Organization (WHO) committee studying the behavioral aspects of mask wearing, such as whether it has an impact on other risky behaviors. "What was apparent was that the people on the WHO committee did not appear to understand the full evidence base," she says. But Greenhalgh persisted, and in early June, WHO, along with the U.S. Centers for Disease Control and Prevention and Public Health England, shifted from claiming masks are potentially harmful to endorsing them. "I think the lesson here is don't give up," she says.

Greenhalgh contends that COVID-19 has made the collaboration of science with the humanities and social sciences all the more vital. Take vaccines, for example. Greenhalgh has enrolled as a test subject for Oxford's promising vaccine candidate and insists that carefully controlled studies are essential before any vaccine is released to the general public. Unlike masks, she notes, vaccines and treatments can have dangerous downsides.

But she's well aware of the human factor: Even the best vaccine will not work if people are too frightened to use it, and she is determined to help mitigate that problem through advocacy and public speaking. Technological innovation, she says, is not enough. Empathy, too, plays a vital role. "Science sits awkwardly in a society where truth no longer matters," she says. "As scientists, our goal must be to cut through the rubbish."

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