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Community Use of Face Masks and COVID-19
TAKE-HOME MESSAGE
- This event study looked at the association between mandated mask wearing and changes in COVID-19 growth rates between March 31 and May 22, 2020. The study found that, on a county level, mandating public use of face masks was associated with a reduction in daily growth rates of the infection. Use of face masks is estimated to represent close to 16% to 19% of the effects of other measures of social distancing, such as bans on large gatherings, sheltering in place, and the like.
- As of May 22, estimates suggest that between 230,000 and 450,000 cases of COVID-19 may have been prevented, depending on when states passed the mandates.
abstract
This abstract is available on the publisher's site.
Access this abstract nowState policies mandating public or community use of face masks or covers in mitigating novel coronavirus disease (COVID-19) spread are hotly contested. This study provides evidence from a natural experiment on effects of state government mandates in the US for face mask use in public issued by 15 states plus DC between April 8 and May 15. The research design is an event study examining changes in the daily county-level COVID-19 growth rates between March 31, 2020 and May 22, 2020. Mandating face mask use in public is associated with a decline in the daily COVID-19 growth rate by 0.9, 1.1, 1.4, 1.7, and 2.0 percentage-points in 1-5, 6-10, 11-15, 16-20, and 21+ days after signing, respectively. Estimates suggest as many as 230,000-450,000 COVID-19 cases possibly averted By May 22, 2020 by these mandates. The findings suggest that requiring face mask use in public might help in mitigating COVID-19 spread. [Editor's Note: This Fast Track Ahead Of Print article is the accepted version of the peer-reviewed manuscript. The final edited version will appear in an upcoming issue of Health Affairs.].
Additional Info
Disclosure statements are available on the authors' profiles:
Community Use of Face Masks and COVID-19: Evidence From a Natural Experiment of State Mandates in the US
Health Aff (Millwood) 2020 Jun 16;[EPub Ahead of Print], W Lyu, GL WehbyFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
A remarkably white-hot topic is around the wearing of face masks for the general public—at times, I’m convinced that one of our “neighborhood social media” platforms has turned entirely into a “who is wearing face masks at what businesses” site. Such social questions aside, relatively few US jurisdictions have mandated the use of face coverings, choosing instead to rely on strong recommendations. But should they?
This paper used the existence of patchwork regulations as a natural experiment to see if the existence of mandates seemed to make a difference in the spread of SARS-CoV-2 in those communities. The mandates were present in 15 states and the District of Columbia between April and most of May 2020. A total of 20 other states had mandates only for specific types of employees (eg, barbers), but they did not include these with the “public mandate” group. The remaining 15 states had no mandates at all during that period. These researchers then examined COVID-19 spread during those weeks.
They found, notably, a decrease in the daily COVID-19 growth rate in those areas of between 0.9 to 2.0 percentage points, which, they estimate, may indicate the prevention of 230,000 to 450,000 cases of COVID-19. Well.
Obviously, having a mandate, enforcing that mandate, and successfully enforcing said mandate are different things, and this study doesn’t take that into account. However, in a pandemic where the drop of half a percentage point can reflect many thousands of cases—and lives—these data would be relatively convincing that face mask mandates do indeed seem to be a reasonable public health precaution that is supported by population-level evidence.
Clinically, support your local public health officials when they even recommend face coverings; and, in your own hospitals and clinics, advocate for the creation or continuation of face covering use by patients, visitors, and staff alike.