From the only randomised controlled study of masks... https://bmjopen.bmj.com/content/5/4/e006577.long https://bmjopen.bmj.com/content/5/4/e006577.long "The ra

From the only randomised controlled study of masks... https://bmjopen.bmj.com/content/5/4/e006577.long https://bmjopen.bmj.com/content/5/4/e006577.long "The rates of all infection outcomes were highest in the cloth mask arm, with the rate of ILI statistically significantly higher in the cloth mask arm (relative risk (RR)=13.00, 95% CI 1.69 to 100.07) compared with the medical mask arm. Cloth masks also had significantly higher rates of ILI compared with the control arm. An analysis by mask use showed ILI (RR=6.64, 95% CI 1.45 to 28.65) and laboratory-confirmed virus (RR=1.72, 95% CI 1.01 to 2.94) were significantly higher in the cloth masks group compared with the medical masks group. Penetration of cloth masks by particles was almost 97% and medical masks 44%."