A Small Data Point about Masks

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June 10, 2020 9:33 a.m.

I’ve been talking about the question of the effectiveness of masking for many weeks now. So I wanted to share one very small data point that I found noteworthy. All the caveats: small sample size, not a controlled tests in any way. Still I found it notable.

A few weeks ago right after Missouri relaxed its COVID restrictions two hair stylists at a salon in Springfield, Missouri came down with COVID. Contact tracing revealed they had potentially exposed about 140 clients and six coworkers. The key data point is that all staff and customers at the salon were wearing masks during the period in question.

Of those 140 clients, 46 came forward to take COVID tests. They were all negative. The rest were quarantined during their possible incubation period. None of them developed the disease. Since those hundred of so people were not tested, it’s possible one or more developed a totally asymptomatic case. COVID tests also have significant numbers of false negatives. So we can’t rule out a few asymptomatic cases in that group. But still, no apparent infections at all and 46 people were actually tested and got negative results.

This obviously doesn’t prove masks work. All or most of the people involved were likely also doing significant hand washing and not touching their faces. It’s also true that not everybody spreads the contagion with equal efficiency. Maybe the two infected hair stylists just weren’t efficient spreaders. Still, this is a significant period of time, with dozens of people. And the contact with coworkers would have been fairly significant and sustained. It is at least surprising that there were no additional infections given the contagiousness of COVID.

One more datapoint for the efficacy of masking – not as a foolproof solution but one that at scale significantly reduces transmisison.

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