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  1. Dunphy, Christopher PhD
  2. Joo, Heesoo PhD
  3. Sapiano, Mathew R. P. PhD
  4. Howard-Williams, Mara JD, MPH
  5. McCord, Russell JD
  6. Sunshine, Gregory JD
  7. Kao, Szu-Yu PhD
  8. Guy, Gery P. Jr PhD
  9. Weber, Regen JD
  10. Gakh, Maxim JD
  11. Ekwueme, Donatus U. PhD


Context: Mask mandates are one form of nonpharmaceutical intervention that has been utilized to combat the spread of SARS-CoV2, the virus that causes COVID-19.


Objective: This study examines the association between state-issued mask mandates and changes in county-level and hospital referral region (HRR)-level COVID-19 hospitalizations across the United States.


Design: Difference-in-difference and event study models were estimated to examine the association between state-issued mask mandates and COVID-19 hospitalization outcomes.


Participants: All analyses were conducted with US county-level data.


Interventions: State-issued mask mandates. County-level data on the mandates were collected from executive orders identified on state government Web sites from April 1, 2020, to December 31, 2020.


Main Outcome Measures: Daily county-level (and HRR-level) estimates of inpatient beds occupied by patients with confirmed or suspected COVID-19 were collected by the US Department of Health and Human Services.


Results: The state issuing of mask mandates was associated with an average of 3.6 fewer daily COVID-19 hospitalizations per 100 000 people (P < .05) and a 1.2-percentage-point decrease in the percentage of county beds occupied with COVID-19 patients (P < .05) within 70 days of taking effect. Event study results suggest that this association increased the longer mask mandates were in effect. In addition, the results were robust to analyses conducted at the HRR level.


Conclusions: This study demonstrated that state-issued mask mandates were associated with reduction in COVID-19 hospitalizations across the United States during the earlier portion of the pandemic. As new variants of the virus cause spikes in COVID-19 cases, reimposing mask mandates in indoor and congested public areas, as part of a layered approach to community mitigation, may reduce the spread of COVID-19 and lessen the burden on our health care system.