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The Twelve Days of Mask Mess: Day 7

For the seventh day of mask mess, we got these:

Doung-ngern et al.

Case-control study of use of personal protective measures and risk for SARS-CoV-2 infection, Thailand. Emerg Infect Dis (2020).

Published in November 2020, this study is a retrospective case-control study following “contact investigations of 3 large COVID-19 clusters in nightclubs, boxing stadiums, and a state enterprise office in Thailand.” It relied on telephone interviews asking contacts to the best of their memories about mask-wearing and frequency during contact with the index patient, as well as hand-washing, social distancing, close contact, sharing the same dishes and cups, etc., and whether the index patient was symptomatic. (They acknowledge “several limitations” of their study, including the “common biases of retrospective case-control studies, including memory bias, observer bias, and information bias.”)

Doung-ngern et al. found lower odds of infection from “maintaining a distance of ?1 m[eter] from a COVID-19 patient” and similar odds of infection from “duration of contact ?15 minutes” than for “wearing a mask all the time during contact with a COVID-19 patient.” They found wearing a mask “sometimes during contact with the COVID-19 patient was not statistically significantly associated with lower risk of infection.” They also tested the odds of infection concerning type of masks worn, finding that medical masks were associated with lower odds of infection when worn during contact with a COVID-19 patient. They calculated slightly lower odds of infection from wearing nonmedical masks, but the upper range of their odds included a higher risk of infection.

Doung-ngern et al. stress “consistent” rather than intermittent mask use around COVID-19 patients and, as has other studies promoted by the Cooper administration, warned about incorrect mask wearing.

Setting is key for infection, Doung-ngern et al. found, especially in the home (see Wang et al. above): “The household secondary attack rate in our study (16.5%) is comparable with ranges reported previously (11%–23%) and relatively high compared with workplaces (4.9%) and other settings (1.4%).” Perhaps for that reason, Doung-ngern et al. find that “quarantine measures can be challenging and sometimes impractical.”

They conclude with could and might,

our findings provide evidence supporting consistent mask-wearing, handwashing, and adhering to social distancing recommendations to reduce SARS-CoV-2 transmission in public gatherings. Wearing nonmedical masks in public could help slow the spread of COVID-19. Complying with all measures could be highly effective; however, in places with a high population density, additional measures might be required.

They also say that “Clear and consistent public messaging” is “essential,” and “particularly for targeting those who wear masks intermittently or incorrectly.”

Does this study support Cooper’s extreme exercise of power?


Probable effects (“could” help slow the spread, “could” be highly effective, etc.) are insufficient for extreme emergency orders. Observational studies as opposed to randomized controlled trials (RCTs) are also unlikely to provide evidence compelling enough for extreme emergency orders because of the many bias problems Doung-ngern et al. cite. They found small effects from concerning the nonmedical masks (i.e., the cloth to homemade “face coverings” that Cooper’s order mandates) with a range that suggested even a greater risk of infection in some instances. That evidence is certainly not compelling enough for extreme emergency orders.

Here again Doung-ngern et al. find the household is the key setting for infections, not workplaces and definitely not other settings. This finding would, if anything, caution against Cooper’s latest “Modified Stay-At-Home” order.

Furthermore, this study specifically cautions against some aspects of mask-wearing inherent in the extents of Cooper’s orders. They cause, for example, restaurant patrons, schoolchildren, people trying to speak clearly, and even governors and health secretaries taking turns at the same microphone for ?15 minutes to resort to regularly donning and doffing masks. This study’s focus on intermittent use seems to miss the cautionary note about long-term use found in other research put forth by the Cooper administration. These aspects are contrary to Cooper’s extreme emergency order.

Click for more of the Twelve Days of Mask Mess series. 

Jon Sanders / Director of Regulatory Studies

Jon Sanders studies regulatory policy, a veritable kudzu of invasive government and unintended consequences. As director of regulatory studies at the John Locke Foundation, Jo...

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