Professional and Home-Made Face Masks Reduce Exposure to Respiratory Infections among the General Population
All types of masks reduced aerosol exposure, relatively stable over time, unaffected by duration of wear or type of activity, but with a high degree of individual variation. Personal respirators were more efficient than surgical masks, which were more efficient than home-made masks. Regardless of mask type, children were less well protected. Outward protection (mask wearing by a mechanical head) was less effective than inward protection (mask wearing by healthy volunteers).
Any type of general mask use is likely to decrease viral exposure and infection risk on a population level, in spite of imperfect fit and imperfect adherence, personal respirators providing most protection. Masks worn by patients may not offer as great a degree of protection against aerosol transmission
A recent analysis of the 1918 epidemic, noted that cities where strict interventions were implemented early on to prevent transmission, were overall worse-off than cities where some degree of transmission occurred early on [16]. Given the need for the population to acquire sufficient natural immunity over time, it can not be excluded that the amount of protection conferred by home made masks might sufficiently reduce viral exposure to impact on transmission during the early waves, while allowing people enough exposure to start mounting an efficient immune response. Further field studies are needed to assess acceptability and effectiveness of masks worn by people from the general population. Also, experimental data are needed to develop dose-response models which may improve understanding of determinants of transmission. A cost-effectiveness analysis might give further insights in the relative benefits of home made masks.
Given the need for the population to acquire sufficient natural immunity over time, it can not be excluded that the amount of protection conferred by home made masks might sufficiently reduce viral exposure to impact on transmission during the early waves, while allowing people enough exposure to start mounting an efficient immune response.
Re: 681 - Thanks for posting this. Suggests that properly fitted masks can provide a benefit.
I thought we read an article (on one of latest CV threads) that said the opposite.
It compared the measures taken between Philly and St Louis...who both had first cases of 1918 epidemic about the same time....
Philly continued on with public gatherings, school openings, etc., while SL stopped all public gatherings, closed schools. The difference in deaths, betweet Ph and SL were about half (Philly having twice as many deaths, than SL).
The measures taken, by SL, were attributed to a doctor who also headed up their health department.