David, Did you scan through his studies? Take another look. They dont read the way Alex claims they read. First, when I looked at Alex's studies I was surprised by how little empirical evidence there is with mask wearing to prevent virus particles from being inhaled or breathed in wearing certain types of masks. Second, Its gets more confusing when we consider the many types of masks used or studied. At best they say the evidence is inconclusive and additional research needs to be done.
Before I dive into it however. Protecting the wearer is not the main rationale for wearing a mask in public. All these studies are about that, protecting the wearer.
Its established that if two people are each wearing a cloth mask the potential for spreading infectious aerosols is greatly diminished. And by the way, Its established that asymptomatic folks can spread the disease, just to be clear.
https://wwwnc.cdc.gov/eid/article/26/7/20-1595_article
The researchers spend considerable print mentioning the difficulty in conducting the studies themselves which also use different research designs. I did not read through them but skipped to the analysis and conclusions. Most of this research is older and done with less contagious viral strains. My argument is there is a confounding threat to application of these studies with colds and flu viruses to SARS-coV2, which although from the same Corona family is a completely different animal.
I posted the most recent study published in June and updated in July 2020 which actually includes the compilation of 39 different investigations and included +33,000 participants. Some of these studies are older but encompasses a wider range of different design types. This study was also not conclusive, and mentions a wide range of different masks were used. If you just scan down to the results. The researchers painstakingly go through all the threats and bias from these various studies. All the studies were conducted in high risk areas i.e. hospitals. Thats a huge bias when looking at in home use, such as grandma wearing a KN 95 mask with the grandkids visiting. Theres a July update which covers home use of masks I copied and paste here
"The original rapid review included 39 studies of mask use for the prevention of viral illness. No studies in the original review assessed the effect of mask use on prevention of SARS-CoV-2 in the community, and 2 observational studies reporting on mask use in health care settings for SARS-CoV-2 prevention had methodological limitations.
The new study added for this update was a retrospective cohort study of 124 households with an index SARS-CoV-2 case and 355 uninfected household contacts (
Supplement Table 1) (2). Households in which masks were used by at least 1 family member (including the index case) before the development of symptoms by the index case were associated with decreased risk for incident infections, after adjustment for other hygiene and infection control practices, physical distance to index case, environmental factors, and presence of diarrhea in the index case (adjusted odds ratio, 0.21 [95% CI, 0.06 to 0.79]) (
Supplement Table 2)."
OK, In retrospect, honestly, if all employees of my facility are wearing different kinds of masks and following other more common protective measures. Then if asymptomatic, they are restricting infectious aerosols into the environment and preventing infection of other employees and more important residents.
I may add, the infectious disease doctor at our facility did not require employees to wear a specific kind of mask. That said if I have an ailing elderly mother in my house. I would take that additional precautions of wearing a mask around her.