Masks made ‘little to no difference’ to Covid infection or death rates, according to one of the most comprehensive meta-analyses of face coverings.
The research – carried out by the Cochrane Institute, the ‘gold standard’ of evidence-based reviews – looked at 78 global studies involving over a million people.
Results indicated that surgical masks reduced the risk of catching ‘Covid or a flu-like illness’ by just five percent – a figure so low it may not be statistically significant.
The researchers said harms caused by masks – including hampering children’s schooling – were poorly measured in the studies, meaning any small benefit on infection rates may be outweighed.
Professor Francois Balloux, a professor of computational biology at University College London, who was not part of the analysis, said it showed that the benefit of wearing masks is ‘at best small’.
In total, the researchers looked at 78 studies involving more than a million people across the world. Results indicated that surgical masks reduced the risk of catching ‘Covid or a flu-like illness’ by just five percent – a figure so low it may not be statistically significant
While initially viewed as a virus prevention measure, masks have become a prominent symbol of the Covid culture wars in the US.
Officials issued mixed messages about their effectiveness at the beginning of the pandemic. Studies that came later failed to show definitively that masks prevented Covid — yet millions of Americans were forced to abide by mandates.
Some of the researchers involved in the Cochrane review previously analyzed the evidence on masks in November 2020.
That review was criticized because it did not include any studies from the Covid pandemic due to limited research at the time.
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A separate Danish study in the spring of 2020 with over 6,000 participants found that wearing a mask made no statistical difference to whether or not people got Covid. But its researchers struggled to find a prominent journal willing to publish the results.
The Cochrane researchers updated their review with 11 additional studies involving more than 600,000 people, bringing the total number of studies to 78. The analysis was published this week in the Cochrane Database of Systematic Reviews journal.
Some of the additional studies looked at Covid, while others were conducted before the pandemic and looked at flu and other respiratory illnesses.
They included Covid pandemic trials – two from Mexico and one each from England, Norway, and Bangladesh, plus the Danish study.
The researchers only added randomized controlled trials (RCTs) looking at the effect of physical interventions to protect against illness, including mask-wearing.
RCTs are the optimal method to prevent systematic differences between participants affecting results. In RCT studies, the mask and control groups are randomly chosen from the same eligible population.
The main outcomes the Cochrane researchers measured were the number of flu- and Covid-like illness cases and any adverse events that came about from the intervention.
The researchers said harms caused by masks – including hampering children’s schooling – were poorly measured in the studies, meaning any small benefit on infection rates may be outweighed
The Cochrane researchers calculated risk ratios relating to mask-wearing.
A value of below one indicates the intervention improved the outcome and a value above one shows it made it worse. The nearer to one the risk ratio value is, the less of an effect it had.
The researchers noted a high risk of bias in the studies and a ‘relatively low adherence with the interventions’, making it difficult to draw firm conclusions.
But Professor Balloux tweeted: ‘Cochrane reviews are the “gold standard” in evidence-based medicine.
‘They follow a rigorous methodology and only consider high-quality evidence. As such, the review included a limited number of studies and has moderate power to detect small effects.
‘Irrespective of the limitations of the study, its results indicate that the true impact of medical/surgical masks and N95/P2 respirators on the transmission of respiratory viruses is at best small.’
To compare the effect of masks on preventing the spread of Covid and flu, the Cochrane researchers looked at 12 trials — two in healthcare workers and 10 in the community.
They found that in the community, wearing a face mask reduced the risk of catching either flu or Covid-like illness by five percent.
The team said both these results were ‘moderate certainty evidence’.
They also looked the effect of higher grade masks such as N95s compared to standard surgical masks but were less sure of their impact.
The CDC only recommended that people wear N95s two years into the pandemic.
This part of the analysis looked at five studies — four in healthcare workers and one in households — with 16,000 participants in total.
They found that wearing a mask reduced chances of clinical respiratory illness by 30 percent.
But Professor Carl Heneghan, of the University of Oxford, who was an unlisted author on the paper, recognized that ‘harms were rarely measured and poorly reported’, meaning it was ‘very low‐certainty evidence’.
N95 masks are even more uncomfortable than surgical masks because of their thick material and tight fit.
Nurses who wore them for long periods of time during the pandemic reported cuts and scarring on their faces as a result.
But this also makes them better at preventing infections than regular surgical masks, which are too porous to block microscopic viral particles passing through.
The debate around masks first turned sour in 2020 when health officials flip-flopped on their effectiveness.
Then-NIAID director Dr Anthony Fauci said in 2020 that masks were ‘not providing the perfect protection that people think that it is’.
He later suggested people should wear masks as a mark of ‘respect’ for others, and admitted to lying to the public about masks’ effectiveness to prevent panic buying and preserve masks for healthcare workers.
The CDC website currently states that masks can help protect the wearer and others from Covid.
The agency is still recommending Americans wear masks in places with high transmission levels, such as on public transport.
Critics of masks claim they have hindered communication and children’s development and progress at school.
Rises in RSV and flu this winter were partly attributed to face-covering mandates because they prevented children from gaining natural immunity to other illnesses.
