What the science says about lifting mask mandates

He and his colleagues used data from 401 regions in Germany to estimate the effect of mask mandates on SARS-CoV-2 transmission3. They took advantage of the regional variation to create artificial controls, and then estimated what would have happened had the intervention not been implemented. His team’s conclusion: requiring people to wear face masks decreases the daily growth rate of reported COVID-19 cases by more than 40%. The economists’ approach was “clever”, says Hoen. “This adds to the body of evidence that masks work.” In a similar study in the United States, published this January5, researchers found that a national mandate for employees to wear face masks early in the pandemic could have reduced the weekly growth rate of cases and deaths by more than 10 percentage points in late April 2020. The study suggests that this could have reduced deaths by as much as 47% (or by nearly 50,000) across the country by the end of May last year. Another preprint, published in October, linked mask mandates with a 20–22% weekly reduction in COVID-19 cases in Canada6. Still, US data suggest that regulation alone might not have been enough to produce a benefit from masks. In a survey of more than 350,000 people, published this March, self-reported mask wearing increased separately from government mask mandates7. The mandates do have an effect, “but when we looked at it, it was really the behaviour of the population that was a better metric”, says John Brownstein, an epidemiologist at Harvard Medical School in Boston, Massachusetts, and a co-author of the study. “There’s a difference between government policy and community buy-in.”