Do face masks work?

Nov 26, 2023

Robert Dingwall

Throughout the Covid-19 pandemic, international agencies, national governments, and local public health departments claimed that their policies followed ‘the science’. The imposition of face masks in public areas was a prominent example.

‘Hands, face, space,’ we were told; the belief was that wearing a mask would prevent the transmission of the SARS-Cov-2 virus. Critics who called into question the evidence for that claim were accused of peddling ‘misinformation’. Yet the latest review of mask wearing studies suggests they were right – and that masks made little to no difference in curtailing the spread of Covid.

When the virus first arrived in the UK in 2020, the official view, based on the science of the time, was that masks had no value outside health care. This verdict drew heavily on the Cochrane Review of physical interventions to interrupt or reduce the spread of respiratory viruses.

The Review strengthens its conclusion to saying there is ‘probably little to no benefit’ from the use of cloth or surgical face masks in the community

Since they started in 1993, Cochrane Reviews have become the international gold standard of evidence for medical practice. They are only published after an exhaustive process of peer review, with full transparency about the way they identify and rate studies to include. They are rightly treated as definitive summaries of the contemporary state of scientific knowledge.

The Reviews give greatest weight to Randomised Controlled Trials (RCTs) as evidence. These have the lowest risk of bias of any epidemiological method. A population is randomly assigned to a group that receives an intervention (e.g. masks) and one that does not (control). In principle, the intervention is the only difference between the groups, eliminating other factors that might confuse the picture. In practice, this is difficult to achieve. Cochrane Reviews deal with that problem by pooling results from different studies in a meta-analysis. Any biases that have crept in are likely to cancel each other out so users can have confidence in the overall result. If RCTs are not available, the Reviews look at other types of study but warn that this is inferior evidence.

Cochrane Reviews have been tracking face masks since 2007, with updates in 2009, 2010, 2011 and 2020. They found only a few, small, RCTs and the evidence base was rated as low quality. Nevertheless, it suggested little or no benefit from masks. The 2020 review repeated earlier conclusions that it was ‘uncertain’ whether community use of cloth or surgical face masks slowed the spread of respiratory viruses.

This scepticism informed the starting position of many experienced public health leaders in 2020. Doubts about the value of masks were not misinformation. Yet this view was reversed for reasons that are not yet fully understood – and debate about mask wearing was largely off limits. Anyone who criticised mask wearing was likely to be branded as a peddler of untruths. Serious questions about the legitimacy of overt state intervention, through law, or covert state intervention, through ‘nudging’, to promote a policy based on ‘uncertain’ evidence were dismissed as fringe libertarianism. Treating all criticism as misinformation, rather than as loyal opposition intended to improve policy and governance, is a throwback to 17th century claims about the right of governments to impose tests of religious belief as a condition of participation in public life.

A further updated Review has just been published, after the usual thorough peer review. More and larger RCTs are now available. The quality of evidence has been upgraded from low to moderate. The Review strengthens its conclusion to saying there is ‘probably little to no benefit’ from the use of cloth or surgical face masks in the community. It also considered N95/FFP2 masks. The evidence was weaker but suggested that these made little or no difference. The Review regrets the absence of funding for additional trials, which would have permitted a stronger conclusion. This reiterates a call that many have been making since summer 2020, which has consistently been ignored by those in a position to fund such studies.

There is now one further report, from a large trial in Guinea-Bissau, in west Africa, in a pre-print that has not yet been peer-reviewed. It has limitations but its results are consistent with the studies included in the Cochrane Review. There is nothing to change the Review's conclusions.

Lacking support from RCTs, mask advocates have shifted their ground to rely on ‘mechanistic’ evidence from physics and engineering, claiming laboratory studies should be judged by different standards. However, such evidence has never led health and safety agencies to recommend even N95/FFP2 masks for protection against respiratory viruses. The RCTs establish the failure of masks once they leave highly-controlled experimental conditions and arrive in the real world.

Some argue that masks should be worn in solidarity with ‘the vulnerable’. Yet if the evidence is that masks are unlikely to work, it is irresponsible to promote a false sense of security – particularly as the definition of ‘vulnerability’ is often very selective. Most people with an immunosuppressive condition will still benefit from vaccination. Others need to act as they did before 2020 to manage their personal risk from any respiratory virus.

Mask mandates were never evidence-based policy. They simply triggered a search for policy-based evidence. My mask never protected you and yours certainly did not protect me.

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Robert Dingwall is Emeritus Professor of Sociology at Nottingham Trent University

Robert Dingwall

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