It’s Eve. Lambert is very pleased that a team led by Oxford University’s Trish Greenhalgh has decisively defeated the bizarre and destructive campaign against mask-wearing, a case in point being the widely publicized and then debunked Cochrane report. Greenhalgh and her fellow scientists took the common-sense step of excluding studies that didn’t study the effectiveness of masks, such as studies that involved people removing their masks when indoors, or, even worse, studies that treated various public efforts at mask-wearing as if they had produced appropriate mask use. A key sentence from this post: “Most of the RCTs on mask-wearing in the general public were actually trials to encourage mask-wearing.”
I was going to embed the following study, which both KLG and Ignacio call excellent, at the end of the post, but the file size is too large. here.
And please spread this post far and wide!
Trish Greenhalgh, Professor of Primary Care Health Sciences, University of Oxford; C. Raina McIntyre, Professor of Global Biosecurity, NHMRC L3 Research Fellow and Head of the Biosecurity Program at the Kirby Institute, University of New South Wales; and David Fisman, Professor in the Department of Epidemiology, University of Toronto. conversation
Time Texas Farm Workers Recently, rumors have circulated on social media about avian flu being transmitted from cows. Although avian flu is not a human pandemic, scientists and policymakers around the world are eager to be as prepared as possible in the event of such a pandemic occurring. tricky This challenge is important given that science is complex, policies must be pragmatic, and people’s values do not always align.
It’s time to talk about masks. In the early stages of a pandemic with a new virus or a new mutation, we may not have a vaccine, no solid knowledge of how bad things will get, or specific treatments. Slowing the spread will be key until more is known.
If most people wore masks, it would slow the spread of infection and potentially prevent or reduce the impact of the pandemic. Wearing a mask is inconvenient, but it’s not as inconvenient as a lockdown.
But do masks work? review Only clinical trials of masks and ventilators were considered Conclusion Some have suggested there is not enough evidence to assess whether wearing a mask reduces the risk of catching or spreading respiratory illnesses. We disagree.
The review, by the not-for-profit Cochrane Consortium, was not able to influence the recently published US guidelines. Centers for Disease Control and Prevention Following alarming news of avian influenza being transmitted to humans, the CDC has recommended that all workers who handle potentially infected cattle wear tight-fitting respirators in addition to overalls and safety goggles until the threat of avian influenza subsides.
Is this updated guidance based on solid evidence? A fresh look at the evidenceYes. Like the Cochrane team, we pooled data from randomized controlled trials (RCTs) and analysed the combined data – a so-called meta-analysis.
Unlike them, we also looked at evidence outside of RCTs, including dozens of laboratory studies showing the spread of respiratory infections like the common cold, COVID, flu, measles and tuberculosis. Mainly through the air.
Laboratory studies have found that different mask materials have different particle filtration capabilities and also different breathability, especially when wet, which could explain why moisture from exhaled air can make damp cloth or paper masks more difficult to breathe through and less protective.
Medical masks are usually worn loosely around the face (allowing air to pass through the filters) Ventilators They should fit snugly and be fit tested if worn at work to ensure all air inhaled or exhaled passes through a quality filter.
All this non-RCT evidence is crucial to the design of RCTs. Because respiratory viruses are airborne, to be most effective a mask must be made of a highly filtering material and fit snugly. Do not remove your mask while indoors, as doing so will quickly expose you to airborne infectious particles.
So we shouldn’t expect to see benefits in RCTs of poorly designed masks, masks that don’t fit well, or masks that are only worn occasionally, and we shouldn’t expect benefits unless the mere advice to wear a mask is followed.
Finally, when comparing respirators to masks, in places with a high risk of infection, such as hospitals, respirators need to be worn continuously. Until people leave the buildingThey are not just worn occasionally when performing so-called “aerosol-generating procedures,” such as intubating a patient.
Taking these important details of RCT design into account, rather than simply comparing masked vs. non-masked trials, would show that masks are effective, and ventilators even more effective, in reducing the spread of respiratory disease, and would also explain why some previous reviews seem to indicate this is not the case.
Most of the RCTs on mask wearing in the general public were actually trials to encourage people to wear masks. Both RCTs and observational studies (like real-world experiments) found a dose-response effect, meaning the more people who wore masks, the more effective they were. And if there’s a pandemic looming, people are more likely to wear masks.
Conclusion
We looked at RCTs and found that masks do provide protection in the community, and that for health care workers, N95 masks (masks made with high-quality filtering material and designed to fit snugly to the face to protect against airborne contaminants) are better than masks, especially when worn continuously in the workplace. Non-RCT evidence also shows that masks are effective, and that masks are more effective.
Let’s hope we don’t see another pandemic. But in the unlikely event that it does, recent reviews have concluded that masks are effective. Along with improving indoor air quality and avoiding crowded, poorly ventilated spaces, masks can help. Avoid respiratory infectionsAnd our findings suggest that rather than just wearing a mask, Wear the best mask available.
