According to one of the most comprehensive meta-analyses of face coverings, masks made “little to no difference” in Covid infection or death rates.
Conducted by the Cochrane Institute, the “gold standard” of evidence-based reviews, the study looked at 78 global studies involving over a million people.
The results showed that surgical masks reduced the risk of contracting “Covid or a flu-like illness” by just five percent – a number so low it may not be statistically significant.
The researchers said the harms caused by masks – including preventing children from attending school – have been poorly measured in the studies, meaning any small benefit can be outweighed by infection rates.
Professor Francois Balloux, a professor of computational biology at University College London, who was not involved in the analysis, said it showed the benefit of wearing masks was “small at best”.
In total, the researchers looked at 78 studies involving more than a million people around the world. The results showed that surgical masks reduced the risk of contracting “Covid or a flu-like illness” by just five percent – a number so low it may not be statistically significant
Although initially seen 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 early in the pandemic. Subsequent studies could not conclusively show that masks prevented Covid – yet millions of Americans were forced to comply with mandates.
Some of the researchers involved in the Cochrane review analyzed the evidence on masks back in November 2020.
This review was criticized for not including studies on the Covid pandemic due to the limited research at the time.
A separate Danish study in spring 2020 with over 6,000 participants found that wearing a mask made no statistical difference in whether people contracted Covid or not. But his researchers struggled to find a prominent journal willing to publish the findings.
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 journal Cochrane Database of Systematic Reviews.
Some of the additional studies looked at Covid, while others were conducted before the pandemic and looked at influenza and other respiratory illnesses.
These included studies on the Covid pandemic – two from Mexico and one each from England, Norway and Bangladesh, as well as the Danish study.
The researchers added only randomized controlled trials (RCTs) examining the effect of physical interventions to protect against disease, including mask wearing.
RCTs are the optimal method to prevent systematic differences between participants from affecting the results. In RCT studies, the mask and control groups are randomly selected from the same eligible population.
The key outcomes the Cochrane researchers measured were the number of flu and Covid-like illness cases and any adverse events caused by the intervention.
The Cochrane researchers calculated risk ratios related to mask wearing.
A score below one indicates that the intervention improved the outcome, and a score above one indicates that it worsened. The closer the risk ratio value is to one, the smaller the effect.
The researchers found a high risk of bias in the studies and “relatively low adherence to 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. Therefore, the review included a limited number of studies and has moderate power to detect small effects.
“Notwithstanding the study’s limitations, its results indicate that the true impact of medical/surgical masks and N95/P2 respirators on respiratory virus transmission is small at best.”
To compare the effect of masks on preventing the spread of Covid and flu, the Cochrane researchers looked at 12 studies – two involving healthcare workers and 10 in the community.
They found that wearing a face mask in the community reduced the risk of contracting the flu or a Covid-like illness by five percent.
The study suggested that wearing a mask actually increases the risk of testing positive by one percent, but the margins are too small to say for sure.
The team said these two results were “evidence-proving”.
They also looked at the effect of high-quality masks like N95 compared to standard surgical masks, but were less sure of their effect.
The CDC only recommended that people wear N95 for two years after the pandemic began.
This part of the analysis looked at five studies—four on healthcare workers and one on households—with a total of 16,000 participants.
They found that wearing a mask reduced the risk of clinical respiratory disease by 30 percent.
But Professor Carl Heneghan of the University of Oxford, who was an unlisted author of 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 due to their thick material and tight fit.
Nurses who wore them for extended periods during the pandemic have reported cuts and facial scars.
But this also makes them better at preventing infection than regular surgical masks, which are too porous to block microscopic virus particles.
The debate around masks first turned sour in 2020 when health officials flipped their effectiveness.
The then NIAID Director Dr. Anthony Fauci said in 2020 that masks “don’t offer the perfect protection that people think.”
He later suggested that people should wear masks as a show of “respect” for others and admitted to lying to the public about the effectiveness of masks in preventing panic buying and obtaining masks for healthcare workers.
The CDC website currently states that masks can help protect the wearer and others from Covid.
The agency still recommends that Americans wear masks in places with high transmission levels, such as on public transportation.
Critics of masks claim they have hindered communication and children’s development and progress in school.
The rise in RSV and flu this winter has been attributed in part to face covering mandates because they prevented children from gaining natural immunity to other diseases.