Mask use is by no means a panacea, and needs to be done in combination with other measures; however, if mask use reached 95%, lockdowns would not be needed.

https://www.euro.who.int/en/about-us/regional-director/statements-and-speeches/2020/statement-situation-update-on-covid-19-doing-our-share,-a-new-horizon-with-technological-and-pharmaceutical-development,-and-preserving-the-rights-of-children