A cyclist wearing face mask is seen near the Brandenburger Gate in Berlin, capital of Germany, March 28, 2020. (Photo by Binh Truong/Xinhua)

The obligation to wear face masks has considerably helped reduce the spread of the coronavirus infection in Germany, according to a discussion paper published by four universities in Germany and Denmark on Monday.

A woman wearing face mask is seen in Berlin, capital of Germany, May 28, 2020. (Photo by Binh Truong/Xinhua)

Comparing data from Jena, the first German city to make the wearing of face masks mandatory, with other cities in the country, the paper found that the face mask obligation had helped reduce the total number of registered COVID-19 cases by between 2.3 percent and 13 percent within 10 days after its introduction.

Mandatory face masks have "contributed to a slowdown in COVID-19 development in Germany," the paper said, reducing the daily growth rate of reported infections in Germany by around 40 percent.

The figure clearly showed a "gradually widening gap" in the cumulative number of COVID-19 cases between Jena and comparable cities without a face mask obligation, according to the paper.

 

A waiter wearing a face mask serves customers at a reopened restaurant in Berlin, Germany, on May 16, 2020. (Photo by Binh Truong/Xinhua)

Twenty days after the introduction of the mask requirement in Jena, the total number of registered cases increased by only 16 instead of 62, which the paper assumed would have been reported without the measure.

"Wearing face masks is a very cost-efficient measure for fighting COVID-19," according to the paper drafted by scientists from the German universities of Mainz, Darmstadt and Kassel, and from Sonderborg University in Denmark.

The scientists also called for "further systematic causal analyses of the different health measures implemented to fight the spread of COVID-19."

A woman wearing face mask is seen in Berlin, capital of Germany, May 28, 2020. (Photo by Binh Truong/Xinhua)