Masks and respirators: Results of a state of the art review

This “State of the Art Review” on the role of masks & respirators in preventing respiratory infection in the BMJ is worth a deep dive. @PrognasticChats did this on Twitter and this is published below (with permission).

Some important messages from the paper are listed below.

Keep it on & it works:

“Continuous & targeted use of respirators found that respirators were considerably more effective than masks if worn continuously…Intermittent use of respirators or medical masks only when performing high risk procedures was not protective“

Respirators are more effective than medical masks:

“Early data on Covid (2020); in a subanalysis, respirators were 96% effective compared with masks, which were 67% effective… The overall protection factor of N95 respirators was 8-12 times greater than that of surgical masks”

Respirators (FFP2/3, N95) are better than surgical masks, which are better than cloth masks, which are better than no masks:

“The most recent community RCT in Norway showed surgical masks were 29% protective against self-reported respiratory symptoms compared with no mask”

“Aerosol studies have reported that the blocking of exhaled aerosols improves with the number of layers of a mask, and is better with a surgical mask than a cloth mask”

Covid can be spread by asymptomatic people & by people before they develop symptoms, so you can’t rely on symptoms to know if someone can infect you:

“Asymptomatic transmission of flu has long been recognized, but Covid has a much higher degree of asymptomatic transmission“

“ It is estimated that 30-50% of SARS-CoV-2 transmission is asymptomatic”

This means if you are out in public or sharing spaces, you have no idea how many around you are spreading covid into the air, masks are needed:

“People who are sick or healthy cannot self-identify risk of exposure in a crowded public setting unless testing is done”

Asymptomatic & presymptomatic Covid spread with no one masking is allowing Covid to have constant waves of infection still:

“This is one of the strongest justifications for mass masking during epidemic waves of SARS-CoV-2” (that is now)

ANY mask is better than no mask:

“The evidence shows that respirators offer better protection than masks, but that any protection is better than none during a pandemic or serious emerging respiratory infection”

How your mask fits your face is key, a tight fit offers better protection:

“A loosely fitted respirator could provide the same protection as a medical mask, while a tightly sealed medical mask or respirator will significantly improve the protection”

Hospitals and masking. I felt this line deep in my soul:

“For a health worker, the hazard is the job itself; they must treat patients with deadly infectious diseases, and removal of these patients or substitution of them is clearly not an option”

Covid spread in hospitals is a huge ongoing issue:

“Nosocomial [hospital acquired] covid is a major, ongoing problem, with a high mortality rate”

“Covid has substantial transmission in the asymptomatic or presymptomatic period, universal masking can have a major impact on flattening the curve”

Masking guidelines in hospital is based on money, not evidence:

“The evidence from healthcare supports N95 use, but continuously rather than occasionally in self-identified situations of risk. Targeted N95 use might be a cost saving measure, rather than evidence based policy“

Changing won’t be easy:

“This will require a major paradigm shift because guidelines to date recommend targeted use of  respirators in very select situations…studies suggest using cheaper, less effective  masks, might end up being costlier in the long run for hospitals”

Conclusion:

“There is ample evidence on the effectiveness of masks & respirators in community & healthcare settings to inform consistent policy. Respirators are superior & should be the 1st choice in a serious emerging epidemic or pandemic in healthcare & aged care settings“

Conclusion:

“Strong leadership is required to overcome politicization & polarization around masks”

Read the full review paper by clicking here.