We studied the real-life effect of an unprecedented rapid mass vaccination campaign. Following a large outbreak of B.1.351 and B.1.1.7/E484K in the district of Schwaz/Austria, 100,000 BNT162b2 doses were procured to mass vaccinate the entire adult population (16+) of the district between the 11th and 16th of March 2021. This made the district the first widely inoculated region in Europe. We examined the effect of this unique campaign on the number of infections including VoCs, hospital and intensive care unit (ICU) admissions. We compared Schwaz with (i) a control group of highly similar districts, and (ii) with populations residing in municipalities along the border of Schwaz which were just excluded from the campaign. We find large and significant decreases for all outcomes after the campaign, including VoCs cases. The reduction relative to the control regions was largest for younger age cohorts, which were mostly non-vaccinated in the rest of the country due to the age-gradient in the national vaccination plan. Our results demonstrate that rapid population-wide mass vaccination can be an effective tool to curb overall infections as well as VoCs.