[blueash]

Originally Posted by golfing eagles

In essence it helps 0%, don't bother buying or wearing one unless you are sick yourself

Then, why do doctors and nursing wear them, and why is there plea for them due to shortage? Why are they ramping up production?

There is a well tested method of scientific evaluation, the grandmother test. If your grandmother knows it's true, then it's true and no further evaluation is needed.

Golfing's pronouncement that they are 0% effective lacks any references. However the major health organizations have said that there is no reason to wear the typical paper surgical mask. However we have all seen the photos especially from Asian communities of large numbers of people wearing surgical masks as they are out and about. It does seem logical that some filtration is better than no filtration. So has this been evaluated and if so what does the data show? Keeping in mind that one study is not proof, you may want to take a look at a few references.

Feb 2009 Emerg Inf Dis

Conclusion in part:

the relative reduction in the daily risk of acquiring a respiratory infection associated with adherent mask use (P2 or surgical) was in the range of 60%–80%. .. We emphasize that this level of risk reduction is dependent on the context, namely, adults in the household caring for a sick child after exposure to a single index case. We urge caution in extrapolating our results to school, workplace, or community contexts, or where multiple, repeated exposures may occur, such as in healthcare settings. The exact mechanism of potential clinical effectiveness of face mask use may be the prevention of inhalation of respiratory pathogens but may also be a reduction in hand-to-face contact. Our study could not determine the relative contributions of these mechanisms.

That study looked at transmission within a home of influenza like illnesses and the decrease in transmission to family members of the illness by having the well members wear no mask, a simple surgical mask, or mask [P2] similar to the N95 but not fitted to the user. The participants did not do a good job of actually wearing their masks, but in the small group that did wear them, both the surgical and P2 masks reduced the spread of illness.

Nov 2009 JAMA

This study compared the efficacy of having nurses in a hospital wear fitted N95 masks vs surgical masks as they cared for patients with influenza like illnesses. Again in this study simple surgical masks worked as well as fitted N95 masks

RESULTS:
Between September 23, 2008, and December 8, 2008, 478 nurses were assessed for eligibility and 446 nurses were enrolled and randomly assigned the intervention; 225 were allocated to receive surgical masks and 221 to N95 respirators. Influenza infection occurred in 50 nurses (23.6%) in the surgical mask group and in 48 (22.9%) in the N95 respirator group (absolute risk difference, -0.73%; 95% CI, -8.8% to 7.3%; P = .86), the lower confidence limit being inside the noninferiority limit of -9%.
CONCLUSION:
Among nurses in Ontario tertiary care hospitals, use of a surgical mask compared with an N95 respirator resulted in noninferior rates of laboratory-confirmed influenza.

So as grandma would have suggested something is better than nothing. And the surprise would be that a simple surgical mask may not be inferior to an N95 mask.

And HERE Is a study from China that had no mask, surgical mask, intermittent fitted N95 use or continuous N95 use in a hospital setting. Only continuous N95 use was strongly beneficial, plus no value to wearing a surgical mask was shown.

For a long list of publications on the topic of face masks click HERE