In a recent opinion piece, Guardian journalist Catherine Bennett makes the claim: ‘evidence has mounted to back mask efficacy’: https://www.theguardian.com/commentisfree/2021/dec/05/refusal-to-wear-a-mask-says-more-about-you-than-your-face-ever-could I emailed her to ask for the references which support her assertion. She responded almost immediately with this list:
1) https://www.pnas.org/content/118/4/e2014564118
2) https://blogs.bmj.com/bmj/2021/09/28/on-the-psychology-and-politics-of-wearing-masks/
3) https://www.poverty-action.org/study/impact-mask-distribution-and-promotion-mask-uptake-and-covid-19-bangladesh
4) https://www.bbc.co.uk/news/health-52945210
Briefly taking each in turn, the first (Howard et al) is almost a year old. It is not an original research paper but based on a literature review. It was not subject to peer review but accepted by one member of the PNAS journal’s editorial board.
Howard et al point out that what is really required to evaluate the efficacy of public mask wearing is ‘a suitably powered randomized controlled trial (RCT), or a suitably powered meta-analysis of RCTs’. However, as they also say, there are neither: ‘… there is no RCT for the impact of masks on community transmission of any respiratory infection in a pandemic’. https://www.pnas.org/content/118/4/e2014564118
As background, they give ‘Wu Lien Teh’s work to control the 1910 Manchurian Plague… in which Wu identified the cloth mask as “the principal means of personal protection.”’ They explain that ‘Wu reported on experiments that showed a cotton mask was effective at stopping airborne transmission, as well as on observational evidence of efficacy for health care workers.’ However, the Manchurian Plague was caused by a bacterium, Yersinia pestis, not a virus https://ajph.aphapublications.org/doi/pdf/10.2105/AJPH.2020.305960. And ‘since … viruses are about 1,000 times smaller than bacteria and are visible only under an electron microscope…’ Wu’s work offers no support for the hypothesis that cloth masks prevent the transmission of viruses. Therefore Bennett cannot use this to support her claim. As a member of ODT has pointed out: ‘…what was effective against bacteria will be like a chain link fence to a virus’.
Howard et al were able to find ‘only one observational study (that) directly analyzed the impact of mask use in the community on COVID-19 transmission.’ https://gh.bmj.com/content/5/5/e002794?ijkey=c2c17aec821e202b8a42b8aeaf612c7f535ce4fc&keytype2=tf_ipsecsha. This study, by Wang et al, claims that face mask use was ‘79% effective in reducing transmission’. However, not only is its methodology highly suspect but it also contains a passage that completely undermines its conclusion:
“As the compliance of UFMU [universal face mask use] would be poor in the home, there was difficulty and also no necessity for everyone to wear masks at home…”
In other words, since the researchers could not guarantee compliance in the home environment, they did not require it – which means that the use of facemasks by family members in the households included in the study was likely sporadic and may not even have happened at all in some households. Given that the study was supposed to analyse the ‘impact of mask use in the community’ its ‘79%’ result is scientifically worthless.
Howard et al include “one controlled trial of mask use for influenza control in the general community…” by MacIntyre et al https://www.ijidonline.com/article/S1201-9712(08)01008-4/fulltext. At one point they claim this research shows “protective efficacy in excess of 80%’. However, when the results are not ‘adjusted’ to show only ‘positive evidence’ it turns out that the 80% figure is simply false:
“We recruited 286 adults with exposure to respiratory infections in the Australian winters of 2006 and 2007 - 94 adults were randomized to surgical masks, 90 to P2 masks and 102 to the control group. Using intention to treat analysis, we found no significant difference in the relative risk of respiratory illness in the mask groups compared to control group.” (italics mine) https://www.ijidonline.com/article/S1201-9712(08)01008-4/fulltext
Howard et al state that ‘evidence from RCTs and observational studies is informative, but not compelling’. Nevertheless they feel able to conclude: ‘The available evidence suggests that near-universal adoption of nonmedical masks when out in public, in combination with complementary public health measures, could successfully reduce Re to below 1, thereby reducing community spread if such measures are sustained.’ https://www.pnas.org/content/118/4/e2014564118
This logic is surely deserving of rigorous journalistic investigation. How can a group of academics write that there is no compelling evidence supporting the use of masks, and provide references that show this, and at the same time propose the ‘near-universal’ use of non-medical facemasks when out in public? This makes no sense.
Bennett’s second reference looks at the psychology of mask wearing from a behavioural science frame which worries that ‘mask wearing is slipping and that it is important to address the factors which impact levels of adherence.’ It is not a scientific paper, it is a blog. It offers no support to Bennett’s claim.
The third reference is a study from Bangladesh which assesses strategies to increase the use of mask wearing. Importantly, ‘the study is not actually a randomised trial of mask-wearing. Rather, it is a randomised trial of mask promotion campaigns. This means that, even if the intervention did have an effect, that effect was not necessarily brought about by more people wearing masks.’ https://dailysceptic.org/2021/09/03/the-bangladesh-mask-study-is-a-missed-opportunity/
The fourth article is a year and a half old and actually shows that WHO advice cannot be taken seriously unless there really is ‘compelling’ scientific evidence rather than a change of opinion by a few unaccountable decision-makers. It says:
“The World Health Organization (WHO) has changed its advice on face masks, saying they should be worn in public where social distancing is not possible to help stop the spread of coronavirus.
The global body said new information showed they could provide 'a barrier for potentially infectious droplets'.
Some countries already recommend or mandate face coverings in public.
The WHO had previously argued there was not enough evidence to say that healthy people should wear masks.”
WHO does not say what this new information is.
Given a serious look at Bennett’s references, it is difficult to see how they can possibly justify the conclusion that ‘evidence has mounted to back mask efficacy’. There is no scientifically rigorous evidence that this is the case, as her references witness. However there is plenty of evidence to the contrary, which she was unable to find via google, or did find and discarded since it does not support her claim:
https://swprs.org/face-masks-evidence/ https://www.professorhinkley.com/blog/sorry-oregon-your-mask-is-useless-according-to-the-science; https://www.city-journal.org/do-masks-work-a-review-of-the-evidence; https://www.cato.org/working-paper/evidence-community-cloth-face-masking-limit-spread-sars-cov-2-critical-review#; https://www.spectator.co.uk/article/do-masks-stop-the-spread-of-covid-19-
David Seedhouse and members of Our Decision Too