  Mass antigen testing has been proposed as a possible cost-effective tool to
contain the Covid-19 pandemic. We test the impact of a voluntary mass testing
campaign implemented in the Italian region of South Tyrol on the spread of the
virus in the following months. We do so by using an innovative empirical
approach which embeds a semi-parametric growth model - where Covid-19
transmission dynamics are allowed to vary across regions and to be impacted by
the implementation of the mass testing campaign - into a synthetic control
framework which creates an appropriate control group of other Italian regions.
We find that the mass test campaign decreased the growth rate of Covid-19 by
39% which corresponds to a reduction in the total additional cases of 18%, 30%
and 56% within ten, twenty and forty days from the intervention date,
respectively. Our results suggest that mass testing campaigns are useful
instruments for mitigating the pandemic.

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