, something public health officials had feared might happen if masks gave people a false sense of security.
The study is"the first large-scale randomized evaluation to demonstrate the effectiveness of masks in a real-world setting," according to IPA. Compared to villages that didn't mask, those where masks of any type were worn had about 9% fewer symptomatic cases of COVID-19. The finding was statistically significant and was unlikely to have occurred by chance alone.
Another reason is that among people who had symptoms, only one third agreed to undergo a blood test. The effect may have been bigger had participation been universal. The investigators also found important differences by age and by the type of mask. Villages where surgical masks were worn had 11% fewer COVID-19 cases than villages in where masks were not worn. In villages where cloth masks were worn, on the other hand, infections were reduced by only 5%.