“Approximately Zero”: What the Best Evidence Shows Masks Do Against Covid

John Tierney has written an excellent article in City Journal summarising the latest Cochrane review showing masks do “approximately zero” against Covid. Here’s an excerpt.

The most rigorous and extensive review of the scientific literature concludes that neither surgical masks nor N95 masks have been shown to make a difference in reducing the spread of COVID-19 and other respiratory illnesses.

This verdict ought to be the death knell for mask mandates, but that would require the Centers for Disease Control (CDC) and the rest of the public-health establishment to forsake ‘the science’ — and unfortunately, these leaders and their acolytes in the media seem as determined as ever to ignore actual science. Before the pandemic, clinical trials repeatedly showed little or no benefit from wearing masks in preventing the spread of respiratory illnesses like flu and colds. That was why, in their pre-2020 plans for dealing with a viral pandemic, the World Health Organisation, the CDC, and other national public-health agencies did not recommend masking the public. But once COVID-19 arrived, magical thinking prevailed. Officials ignored the previous findings and plans, instead touting crude and easily debunked studies purporting to show that masks worked.

The gold standard for medical evidence is the randomised clinical trial, and the gold standard for analysing this evidence is Cochrane (formerly the Cochrane Collaboration), the world’s largest and most respected organisation for evaluating health interventions. Funded by the National Institutes of Health and other nations’ health agencies, it’s an international network of reviewers, based in London, that has partnerships with the WHO and Wikipedia. Medical journals have hailed it for being “the best single resource for methodologic research” and for being “recognised worldwide as the highest standard in evidence-based healthcare”.

It has published a new Cochrane review of the literature on masks, including trials during the COVID-19 pandemic in hospitals and in community settings. The 15 trials compared outcomes of wearing of surgical masks versus wearing no masks, and also versus N95 masks. The review, conducted by a dozen researchers from six countries, concludes that wearing any kind of face covering “probably makes little or no difference” in reducing the spread of respiratory illness.

This may seem counterintuitive, writes Tierney, but not if you understand what’s going on at a microscopic scale.

It may seem intuitive that masks must do something. But even if they do trap droplets from coughs or sneezes (the reason that surgeons wear masks), they still allow tiny viruses to spread by aerosol even when worn correctly — and it’s unrealistic to expect most people to do so. While a mask may keep out some pathogens, its inner surface can also trap concentrations of pathogens that are then breathed back into the lungs. Whatever theoretical benefits there might be, in clinical trials the benefits have turned out to be either illusory or offset by negative factors. Oxford’s Tom Jefferson, the lead author of the Cochrane review, summed up the real science on masks: “There is just no evidence that they make any difference. Full stop.”

This lack of evidence would be enough to keep any new drug or medical treatment from being approved — much less one whose purported benefits had not even been weighed against the harmful side-effects. As the Cochrane reviewers disapprovingly note, few of the clinical trials of masks even bothered to collect data on the harmful effects on subjects. Most public-health officials and journalists have ignored the downsides, too, and social-media platforms have censored evidence of those harms. But there’s no doubt, from dozens of peer-reviewed studies, that masks cause social, psychological, and medical problems, including a constellation of maladies called “mask-induced exhaustion syndrome.”

Tierney notes that, despite all the data showing that COVID-19 poses virtually no risk to healthy children, “the CDC continues to recommend masking all [schoolchildren] in communities where infection rates are rising” and even “cruelly recommends masking everyone from age two on up”.

Incredibly, CDC Director Rochelle Walensky, when asked about the Cochrane studt at a congressional hearing, said: “Our masking guidance doesn’t really change with time. This is an important study but the Cochrane review only includes randomised clinical trials, and, as you can imagine, many of the randomised clinical trials were for other respiratory viruses.”

Tierney notes this is a statement “remarkable for its chutzpah as well as its scientific incoherence”.

One of the worst mistakes of the CDC and other lavishly funded federal agencies was the failure to conduct randomized clinical trials to determine whether their policies were effective. The Cochrane review had to rely on pandemic mask trials conducted in other countries — and now Walensky has the gall to complain that other countries didn’t do enough of the research that U.S. agencies shirked. She’s right that some of the trials involved other viruses, but why dismiss them as irrelevant to the coronavirus? And while one can always wish for more studies to include in a meta-analysis, that’s no excuse to ignore the best available evidence in favor of the shoddy science peddled by her agency to defend its policies.

Data analyst Ian Miller – author of Unmasked: The Global Failure of Covid Mask Mandates – prepared a graph for a previous City Journal article that Tierney reproduces in his article “because it’s a visual confirmation — from nationwide data, not clinical trials — of the conclusions in the Cochrane review”.

Worth reading in full.

Stop Press: Carl Heneghan and Tom Jefferson have written a post on their Substack about the reaction to the recent update of their Cochrane Review.