It is May, 2021. We have 15 months worth of real world data.
Did they look at any real world data? NO.
They created yet another model to prove face masks work.
For this to be published in May 2021 is terrible “science”.
Airborne transmission by droplets and aerosols is important for the spread of viruses. Face masks are a well-established preventive measure, but their effectiveness for mitigating SARS-CoV-2 transmission is still under debate. We show that variations in mask efficacy can be explained by different regimes of virus abundance and related to population-average infection probability and reproduction number. For SARS-CoV-2, the viral load of infectious individuals can vary by orders of magnitude. We find that most environments and contacts are under conditions of low virus abundance (virus-limited) where surgical masks are effective at preventing virus spread. More advanced masks and other protective equipment are required in potentially virus-rich indoor environments including medical centers and hospitals. Masks are particularly effective in combination with other preventive measures like ventilation and distancing.
We now have data from cities, counties, states and entire nations that have had mask mandates. What does the real world data tell us?
Apparently science no longer needs data. All we need is a computer model to prove anything we want to prove. Which is precisely the problem.