At the beginning of the pandemic health officials were hesitant about the masks. The World Health Organization, for example, even recommended until June 2020 that non-infected people do not used, with the argument that they served only so that the infected would not spread the virus: avoid the exit, not the entrance.
Today, masks are mandatory in most of the country, regardless of infection status. Despite the physical plausibility — tennis balls can pass through the holes of a soccer net, but they pass less than if there was no net — there were still many doubts at the beginning of the pandemic about the real effectiveness of the masks. Some feared that they gave a false sense of security, motivating people to adopt other risky behaviors. These doubts finally began to be resolved by more rigorous studies.
The journal Science published earlier this month a study of the Yale economics professor Jason Abaluck, and partners, involving 540 rural villages in Bangladesh, a total of more than 330 thousand people. The study lasted two months, between 900 and 2021, during which infections in the country reached 12 thousand cases per day. Scientists encouraged universal use of masks, rather than just among the symptomatic, with different educational campaigns in a randomly chosen part of villages, and also tested the difference between fabric masks (200 villas) and surgical masks (95 villas).