Study: Mask mandates did not lower case growth during surges

"Maximum case growth was the same among states with early, late, and no mandates..."

A study published by MedRXiv on May 25, 2021, concluded that mask mandates did not slow the spread of COVID-19 during surges. The study is not peer-reviewed.

Link to the study:

Mask mandate and use efficacy in state-level COVID-19 containment

The study was conducted by Damian D. Guerra,  Department of Biology at the University of Louisville in Louisville, Kentucky, and Daniel J. Guerra, Authentic Biochemistry, VerEvMed, in Clarkston, Washington.

Summary of the study:

Background: Containment of the COVID-19 pandemic requires evidence-based strategies to reduce transmission. Because COVID-19 can spread via respired droplets, many states have mandated mask use in public settings.  Randomized control trials have not clearly demonstrated mask efficacy against respiratory viruses, and observational studies conflict on whether mask use predicts lower infection rates. We hypothesized that statewide mask mandates and mask use are associated with lower COVID-19 case growth rates in the United States. 

Methods: We calculated total COVID-19 case growth and mask use for the continental United States with data from the Centers for Disease Control and Prevention and Institute for Health Metrics and Evaluation. We estimated post mask mandate case growth in non-mandate states using median issuance dates of neighboring states with mandates.   

Results: Case growth was not significantly different between mandate and non-mandate states at low or high transmission rates, and surges were equivocal. Mask use predicted lower case growth at low, but not high transmission rates. Growth rates were comparable between states in the first and last mask use quintiles adjusted for normalized total cases early in the pandemic and unadjusted after peak Fall-Winter infections. Mask use did not predict Summer 2020 case growth for non-Northeast states or Fall-Winter 2020 growth for all continental states. 

Conclusions: Mask mandates and use are not associated with slower state-level COVID-19 spread during COVID25 19 growth surges. Containment requires future research and implementation of existing efficacious strategies. 

Citation from the study:

 "Contrary to our hypothesis, early mandates were not associated with lower minimum case growth (Mann-Whitney p=0.087; Fig 1C). Maximum case growth was the same among states with early, late, and no mandates (ANOVA p=0.29; Fig 1D). This indicates that mask mandates were not predictive of slower COVID-19 spread when community transmission rates were low or high." 

A related study from July 19 shows children positive for COVID in schools in Zurich, Switzerland could be explained by community transmission rather than intra-class transmission.

In other words, they picked it up outside of school.

"Conclusions By March-April 2021, 16.4% of children and adolescents were seropositive in the canton of Zurich, Switzerland. The majority of clusters of SARS-CoV-2 seropositive children in school classes could be explained by community rather than intra-class transmission of infections. Seroprevalence and clustering was lowest in upper school levels during all timepoints."

Related reading:

Johns Hopkins Study Found Zero COVID Deaths Among Healthy Kids
Study: Any COVID-19 infection in children leaves strong antibody levels
The Flimsy Evidence Behind the CDC’s Push to Vaccinate Children

North Carolina related reading:

What do Cooper’s 12 mask order extensions all have in common?