Scientists have actually randomized people to wear N95 or regular surgical masks, then tracked how many people got infected with colds and flus similar to the coronavirus. This data can tell us whether N95 or surgical masks are more effective at preventing transmission of viruses. The results surprised me.
People’s Intuitions About N95 Masks and The Coronavirus
Similarly, a doctor interviewed on CNN said that masks don’t work.back to menu ↑
I polled people on Twitter to see what people guessed. A majority (68%) guessed N95, so I’m not alone in my intuition.
But when the data came back, it turned out that rates of infection were the same!
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OK, Maybe That Study Was a Fluke
Again, no significant difference! Both masks performed just as well at preventing the transmission of the viruses. About 9% percent of nurses wearing surgical masks got sick versus 10% wearing N95 masks.back to menu ↑
Entirely Reasonable Skepticism
At this point, there must be at least a few savvy readers thinking, “aha!”
I know what’s going on! These studies didn’t have a control group, so we don’t know whether the masks actually worked. If they both don’t work, then of course there’s no significant difference!
That’s a great question. It’s just hard to test because, what are we going to do? Assign nurses to NOT wear masks? That seems irresponsible.
The No-Mask Test on Viruses
Researchers in Australia studied parents taking care of their children, who were sick with the flu.
Because people often don’t wear masks at home (even around sick people), researchers could defensibly randomly assign people to wear masks or not. They randomly assigned parents to wear no mask, a surgical mask, or an N95 mask like the one I’m wearing here.
Then they tracked how many parents got the flu.
About 16% of parents not wearing a mask got sick, compared to 8% in the surgical and N95 mask groups (called “P2” masks in Australia). Thus, masks seemed to work! But again, surgical masks were just as effective as N95 masks. And the effect size was fairly large—half the infection rate.back to menu ↑
OK, at this point, there must still be some skeptical readers out there. There’s no way that surgical masks can capture particles that small! I saw a doctor on Quora say that “most masks” can’t capture particles the size of viruses.
But when we ignore our intuition and look at actual test data, reality is far more interesting. Test data shows surgical masks are surprisingly effective, even for tiny particles. For example, in one study, researchers tested particles down to .007 microns (even smaller than viruses) and found that a simple surgical mask blocked 80%.
So it’s downright surprising that surgical masks are just as effective! Maybe virus particles are actually easy to capture because they fly on water droplets. Or maybe mask usage prevents people from touching their mouth and nose. For now, I can only speculate.
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