The compulsory use of face masks could slow the spread of the coronavirus by as much as 40 percent, according to a new report.
Scientists from Johannes Gutenberg University Mainz and the University of Southern Denmark studied the German city of Jena, which became the first in Germany to make wearing the face coverings mandatory for citizens riding trains, buses and going into stores on April 6.
The number of new COVID-19 infections recorded in the city then fell by 23 percent over the next 20 days, the study found.
When collating data from the other regions, the researchers said they found a strong curve-flattening effect, concluding that wearing face masks reduces the daily growth rate of reported coronavirus infections by around 40 percent.
“This is a sizeable effect. Wearing facemasks apparently helped considerably in reducing the spread of Covid-19,” they wrote in a discussion paper, published for the Institute of Labour Economics.
“The most convincing argument stresses that Jena introduced face masks before any other region did so,” the paper went on.
“It announced face masks as the first region in Germany while in our post-treatment period no other public health measures were introduced or eased. Hence, it provides the most clear-cut experiment of its effects.”
Jeremy Howard, a research scientist at the University of San Francisco who was not involved in the research, told The London Times that the results were significant.
“You can see the dramatic and sudden divergence between Jena, and the average of other regions that had previously had similar results,” he said.
But Antonio Lazzarino, from University College London, said he is skeptical.
“This is a non-experimental study, so causal inference cannot be claimed,” he told The Times.
There are “too many assumptions,” he said.