How Well Do Masks Work for Preventing Respiratory Disease?

In Massachusetts, all schools were required by the state to have mandatory masking and that was in place just everywhere from September through February of this year. At the end of February, the state announced that school districts could now decide whether or not schools in their district would mask or not masks. And so we ended up looking just at the greater Boston area because that's a much more sort of similar area in terms of density and kind of easier to compare versus thinking about some districts out in Western Massachusetts. Even if some districts, school districts had sort of consistently more cases, that the patterns over time and how the cases went up and down were very similar.