So typical of modern medicine: one day a study says “try this”, the next week a new study says, “no, try that!” I am now guilty of the same thing. A month ago I quoted a study that said regular surgical masks didn’t work well against viruses. Well…now, of course there’s a new study which says they work just as well as N95 masks to prevent the flu.  This study followed 446 nurses during flu season with sick patients, and found that:

…the incidence of laboratory-confirmed influenza was similar between groups (23.6% and 22.9%). In addition, no significant between-group differences were noted in the incidence of influenza-like illness or infections with respiratory syncytial virus, metapneumovirus, parainfluenza viruses, rhinovirus-enterovirus, or coronaviruses…

The study also noted the surprisingly low rate of flu vaccination among the nurses, only 30%. I figured that this group would be much more motivated to get the annual shot, so this shows just how difficult vaccination programs are to enact.

Real Life Results?

One small but fun study followed Beijingers around Second Ring Road with and without an N95 mask, and found a slight rise in blood pressure among the maskless, as well as decreased heart variability. These possibly may be risk factors for the well documented increased heart attacks and strokes during severely polluted days. The study also had an interesting graph (below) which showed that the N95 mask (in red box) really does an outstanding job at filtering pollution (only 3% penetrance), much better than a surgical mask (20%) or handkerchief (72%).

Another very interesting finding was that their 4 categories of cyclist masks  had pollution penetrance rates of  14, 15, 17 and 45%. These are the same or worse as a simple surgical mask, and none were nearly as good as the N95 mask. The study did not mention which specific cyclist masks were tested.

Pollution Penetrance Rates of Different Masks

Article: Surgical Masks or N95 Respirators for the Flu? – Infectious Diseases.

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