Do you dispute these facts?
It didn’t consider how COVID spreads and how masks work
COVID, along with influenza and many other respiratory diseases, is transmitted primarily
through the air.
Respirators (such as N95s) are designed and regulated to prevent airborne infections by fitting
closely to the face to prevent air leakage and by filtering out 95% or more of potential infectious particles.
In contrast, surgical masks are designed to prevent splatter of fluid on the face and are loose-fitting, causing unfiltered air to leak in through the gaps around the mask. The filtration of a surgical mask is not regulated.
In other words, respirators are designed for respiratory protection and cloth and surgical masks are not.
The review starts with an assumption that masks provide respiratory protection, which is flawed. An understanding of these differences should inform both studies and reviews of those studies.
Do you dispute these facts??
Most trials addressed only half the question
Face masks and respirators work in two ways: they protect the wearer from becoming infected
and they prevent an infected wearer from spreading their germs to other people.
Most RCTs in this Cochrane Review looked only at the former scenario, not the latter. In other words, the researchers had asked people to wear masks and then tested to see if those people became infected.
A previous
systematic review found face masks worn by sick people during an influenza epidemic reduced the risk of them transmitting the infection to family members or other carers. Preventing an infection in one person also prevents onward transmission to others within a closed setting, which means such RCTs should use a special method called “cluster randomisation” to account for this.
Data from a RCT of N95 respirator use by
health workers showed even their unmasked colleagues were protected. Yet some of the trials included in the review did not use cluster randomisation.