British surgeon, Joseph Lister, suggested in 1867 that wound infections were caused by the microscopic entities described by Louis Pasteur. From 1897, surgeon Johann Mikulicz of the University of Breslau (now Wroclaw, Poland) wore a face mask during operations and a study of more than 1000 photographs of surgeons in operating theatres in US and European hospitals between 1863 and 1969 showed ‘that by 1923 over two- thirds of them wore masks and by 1935 most of them were using masks’ (Strasser and Schlich, 2020).
By the spring of 2020 most of us were using masks, too, as the COVID-19 era began. However, as the post-pandemic dust settles it appears that the evidence for and against the use of masks has been recruited to serve diverse agendas, whether political or scientific.
In April 2020 the Scottish Government's National Clinical Director, Professor Jason Leitch, asserted that ‘the global evidence is masks in the general population don't work’ (BBC News, 2020); yet in May 2020 a cross- sectional survey of 206 UK community pharmacists found that 72% wore an N95 protective mask and 28% wore protective gloves and apron ‘in addition to safe distancing and protective masks’ (Zaidi and Hasan, 2021).
In August 2020 England's Deputy Chief Medical Officer, Jennie Harries, was clear that ‘the evidence on face coverings “is not very strong in either direction”’ (Pyman, 2020). Meanwhile, Taiwan's 6336 special community pharmacies served as mask- selling sites, representing ‘a new and innovative engagement of pharmacists in public health promotion and protection initiatives’ (Lin et al, 2020).
To what extent are such new and innovative initiatives worthwhile if the supporting evidence is open to challenge? One of the few randomised controlled trials of mask wearing was conducted in a Danish community setting and found that a recommendation to wear a surgical mask when mixing with others outside the home ‘did not reduce, at conventional levels of statistical significance, incident SARS-CoV-2 infection compared with no mask recommendation’ (Bundgaard et al, 2020).
Judging the Danish trial to be inconclusive, Abbasi (2020) considered the influential role of social media in shaping opinion on what was becoming an increasingly contentious issue. There is no doubt that disagreement over the interpretation of peer-reviewed studies is central to the very nature of scientific discourse. However, Abbasi (2020) makes the important observation that the social media platform Facebook – while allowing statements about, for example, injecting bleach to prevent COVID-19 – marked a repost of a Spectator article on the Danish study by a clinical epidemiologist and a professor of evidence-based medicine at the University of Oxford (Heneghan and Jefferson, 2020) as ‘misinformation’ (Abbasi, 2020).
More recently, a Cochrane Review, undertaken by Jefferson et al (2023), evaluated the evidence on wearing medical or surgical masks, and considered 10 community-based studies and two studies in healthcare workers. They found that ‘[c]ompared with wearing no mask in the community studies only, wearing a mask may make little to no difference in how many people caught a flu-like illness/ COVID-like illness … and probably makes little or no difference in how many people have flu/COVID confirmed by a laboratory test …’ (Jefferson et al, 2023).
Further, in a poster presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID), Paterson et al (2023) describe how they analysed infection control data on nosocomial SARS-CoV-2 infection over a 40-week period from a large London hospital and ‘found no evidence that a mask policy significantly impacts the rate of nosocomial SARS-CoV-2 infection with the Omicron variant.’
Yet a political economist (Fumagalli, 2023), presents his defence of a systematic case for mask wearing mandates, with one strand of his argument asserting that such mandates ‘provide a more effective, just and fair way to tackle the ongoing COVID-19 pandemic than policy alternatives such as laissez-faire approaches, mask wearing recommendations and physical distancing measures.’
While Fumagalli's perspective is undoubtedly thought-provoking it fails to take account of those studies – including Cochrane reviews – that have approached the topic of mask wearing from a virological perspective.
With UK public inquiries under way into the handling of the COVID-19 pandemic, it will be interesting to learn about the extent to which evidence on mask wearing shaped the opinions of those politicians and so-called experts whose actions were to influence the behaviour of so many.