NIH.GOV:

Conclusions:
There was no reduction in per-population daily mortality, hospital bed, ICU bed, or ventilator occupancy of COVID-19-positive patients attributable to the implementation of a mask-wearing mandate.

San Antonio mask study, US Army Institute of Surgical Research:

"No reduction in per-population daily mortality, hospital bed, ICU bed, or ventilator occupancy of COVID-19-positive patients attributable to the implementation of a mask-wearing mandate."https://t.co/1gzm8m9pGz

— Phil Kerpen (@kerpen) September 7, 2021

FEE: 

A new study published in the The Southern Medical Journal (SMJ) found that a county-wide mask order in Bexar County, Texas, did not lead to a reduction in COVID-19 hospitalization rates or deaths.

The study, which was peer reviewed, analyzed data before and after mandates were imposed at both the state level (July 3, 2020) and in Bexar County (July 5, 2020), Texas’s fourth largest county.

“We defined the control period as June 2 to July 2 and the postmask order period as July 8, 2020–August 12, 2020, with a 5-day gap to account for the median incubation period for cases; longer periods of 7 and 10 days were used for hospitalization and ICU admission/death, respectively,” the study authors wrote. “Data were reported on a per-100,000 population basis using respective US Census Bureau–reported populations.”

Authors of the study, which was reviewed by the US Army Institute of Surgical Research, analyzed the daily average number of COVID-19 cases, hospitalizations, ICU visits, patients on ventilators, and deaths, and concluded the policy did not reduce any of these metrics.

“All of the measured outcomes were higher on average in the postmask period as were covariables included in the adjusted model,” the researchers said. “There was no reduction in per-population daily mortality, hospital bed, ICU bed, or ventilator occupancy of COVID-19-positive patients attributable to the implementation of a mask-wearing mandate.”