A REVIEW OF scientific research on preventing respiratory diseases did not prove, as has been claimed online, that wearing masks is useless against Covid-19. However, it also failed to show a measurable effect from interventions like mask wearing on reducing the spread of disease.

Despite being the focus of policy and health debates, the effectiveness of mask mandates to stop disease, such as Covid-19 and the flu, has yet to be shown with “large, well designed” randomly controlled trials, the researchers said.

The review was released by Cochrane, a well-respected healthcare research network, and collated data from 78 trials that looked at how to prevent the spread of diseases like influenza and Covid-19.

Critically, much of the data relates to trials ran before the 2020 pandemic. Further, many of them looked at the effectiveness of directing people to wear masks, rather than the mask-wearing itself. 

The 2022 review was just the latest of a series, and includes the analysis of 11 new trials in addition to the 67 they had already reviewed, as of November 2020. 

Both these reviews found similar results, and even included identical phrases in their conclusions.

“There is uncertainty about the effects of face masks,” both reports say, as well as the warning: “The high risk of bias in the trials, variation in outcome measurement, and relatively low adherence with the interventions during the studies hampers drawing firm conclusions.”

Both reports also were unable to find a clear reduction in respiratory infection from orders to wear masks, though a small reduction in respiratory infections was detected when people were told to wash their hands (though this may not be statistically significant when looking at its ability to prevent individual disease types, they noted).

The Cochrane review also listed possible reasons why the studies did not detect an effect, and noted that “relatively low numbers of people followed the guidance about wearing masks”, which may have “affected the results of the studies”.

Despite the limitations of the review, it has been cited online as “proof” that face masks don’t work, including by Ivor Cummins, an Irish commentator who has regularly spread untrue claims about Covid-19.

“Masks are now consigned to the dustbin of scientific history,” Cummins wrote on Facebook, linking to a YouTube video he made. “Case is closed guys – as if it was ever open.”

Other Facebook users spread the link using stronger language: “Chuck the masks and hang the criminal politicians,” one wrote.

Cummins’ YouTube video, called “Case Closed on Masks – Final Proof is in – and its [sic] Over!” has been viewed more than 41,000 times.

In it, Cummins says the report shows it is scientifically certain that wearing masks doesn’t help for respiratory infections. He also says people who think masks work as a health measure are delusional and that the report means he has been “proven utterly correct on everything”.

“I don’t like stating things unequivocally in anything scientific,” he says. “But here, with 78 studies and loads more real-world data, you can state it clear-as-day: masks are junk science.

“That will never change. If you do a thousand more studies, that will never change. That’s it folks.”

However, this is directly contradicted in the Cochrane report itself. The report’s so-called Plain Language Summary puts it succinctly: “We are uncertain whether wearing masks or N95/P2 respirators helps to slow the spread of respiratory viruses based on the studies we assessed.”

It also clarifies: “The results might change when further evidence becomes available. Relatively low numbers of people followed the guidance about wearing masks or about hand hygiene, which may have affected the results of the studies.”

Cummins also misrepresents earlier reviews in the same series to make the case that governments should never have considered masks as a public health measure.

He shows onscreen the 2011 version of the review and claims that this says there was “no evidence worth a toss to support masks”. But that is not what that report says.

Even the text from the 2011 report shown on screen in his video reads: “Implementing barriers to transmission, such as isolation, and hygienic measures (wearing masks, gloves and gowns) can be effective in containing respiratory virus epidemics in hospital wards.”

The full 2011 report goes on to recommend “barrier measures such as gloves, gowns and masks with filtration apparatus” as “effective interventions [...] to reduce transmission of viral respiratory disease”.

Further issues in the most recent report were highlighted by health experts who noted that it mixed results from studies taken in very different settings and that measured different things – some looked at the effect of wearing masks at all times, others at only wearing them part of the time.

The epidemiologist Gideon Meyerowitz-Katz noted on Twitter that if you only counted the trials in the review that were conducted during the Covid-19 pandemic, it would show a detected effect for orders to wear masks.

The Cochrane report itself said that the studies analysed were carried out in different periods, over a course of different pandemics, epidemics and flu seasons.

“Many studies were conducted in the context of lower respiratory viral circulation and transmission compared to Covid‐19,” the report reads.

“The included studies were conducted in heterogeneous settings, ranging from suburban schools to hospital wards in high‐income countries; crowded inner city settings in low‐income countries; and an immigrant neighbourhood in a high‐income country.

“Adherence with interventions [such as mask-wearing] was low in many studies.”

Which-way transmission?

Critics of the study also noted that the review focused on whether mask wearers became infected instead of whether masks stop the spread of germs from the wearer to other people.

(Cluster trials were included in the review, where groups were instructed to wear masks. The review authors say these trials should give a measure of this effect. However, only six of the 78 trials were assessed for masks effectiveness at stopping the onward spread of disease, and one of these was excluded from the meta analysis due to methodological issues.)

The ability for masks worn by infected people to stop the spread of disease to others had been a primary justification for the use of masks by the general public since near the start of the pandemic.

Health experts also emphasised that the review wasn’t related to the theoretical ability of masks to stop disease when worn consistently or correctly, but rather of studies on the effectiveness of interventions/orders to tell people to wear masks.

That effectiveness is impacted by how often participants put masks on; or if they wore them correctly; or if groups not told to wear masks wore them anyway or took other precautions; or if groups who were told to wear them became more reckless in other ways.

The World Health Organization, the Centres for Disease Control and Prevention (CDC) in the US, and the Health Service Executive (HSE) – as well as other bodies around the world – all recommended the use of masks to help curb the spread of Covid-19.

There is scientific evidence other than these randomly-controlled trials that show masks can help to reduce the spread of infections, and since the start of the pandemic, a range of studies, including lab tests and observational studies, have been carried out on masks’ effectiveness against Covid-19 and other viruses.

The virus spreads between people from an infected person’s mouth or nose in “small liquid particles when they cough, sneeze, speak, sing, or breathe heavily”, according to the WHO.

“Other people can catch Covid-19 when the virus gets into their mouth, nose or eyes, which is more likely to happen when people are in direct or close contact (less than one metre apart) with an infected person.”

A study published in September 2020 tested different types of common disposable masks and cloth masks, especially ones from common fabrics that could be used if there was a shortage of other masks, like surgical masks.

It recommended that cloth masks which have multiple layers and use a blend of different fabrics are the most effective, particularly ones which have an inner layer of cotton or linen, a blended middle layer, and an outer layer of polyester or nylon.

Another study, which was published in October 2020, outlined that cloth masks are not the optimal mask type for healthcare workers, who should ideally use a medical or surgical mask, but that they are useful in a community setting to prevent the spread of infection.

Since then, other studies have recommended the use of higher-grade masks following the spread of the more transmissible Omicron variant and its sub-variants.

In February 2022, the US-based Centres for Disease Control and Prevention (CDC) published its own study on the use of face masks and respirators (such as N95 masks).

It found a that the consistent use of a face mask or respirator in indoor public settings “was associated with lower odds” of a positive Covid-19 test result.

“Use of respirators with higher filtration capacity was associated with the most protection, compared with no mask use,” it read.

Update: Cochrane has since confirmed that their study should not be interpreted to mean wearing masks is useless to prevent the spread of Covid-19.

“Many commentators have claimed that a recently-updated Cochrane Review shows that ‘masks don’t work’, which is an inaccurate and misleading interpretation”, a statement released by Cochrane said.

“It would be accurate to say that the review examined whether interventions to promote mask wearing help to slow the spread of respiratory viruses, and that the results were inconclusive.

“Given the limitations in the primary evidence, the review is not able to address the question of whether mask-wearing itself reduces people’s risk of contracting or spreading respiratory viruses.”

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