In the non-face mask group, 2.1 percent of participants were infected with new coronavirus, while 1.8 percent of participants in the face mask-wearing group were infected.

That difference is not big enough to conclude with certainty a benefit of using face masks with regard to protecting oneself from infection.

The researchers stressed that there are limits to the conclusions that can be drawn from the results.

To be more precise: "the results could suggest a moderate level of protection of 15-20 percent"
“The study thereby fails to confirm the expected halving of risk of infection for the wearer of the face mask, but the results could suggest a moderate level of protection of 15-20 percent,” the Danish-language press statement notes.

“According to the study authors, their findings offer evidence about the degree of protection mask wearers can anticipate in a setting where others are not wearing masks and where other public health measures, including social distancing, are in effect,” reads the English-language counterpart.

“The findings, however, should not be used to conclude that a recommendation for everyone to wear masks in the community would not be effective in reducing SARS-CoV-2 infections, because the trial did not test the role of masks in source control (transmission from an infected person to others) of SARS-CoV-2 infection,” it adds.