Austria[0] and Germany[1, edit: this seems to only be true for Bavaria and Berlin, see comments below] have mandated the use of FFP2 masks since the end of January. Their neighboring countries didn't[2].

If you look at the data, there does not appear to be a decrease in infection numbers relative to their neighbors after the switch to FFP2[3].

[0] https://orf.at/stories/3197782/

[1] https://www.focus.de/finanzen/recht/verschaerfte-massnahmen-...

[2] https://www.npr.org/sections/coronavirus-live-updates/2021/0...

[3] https://ourworldindata.org/explorers/coronavirus-data-explor...