APR 06, 2020
In this randomized control trial from 2015, investigators examined the efficacy of cloth masks versus surgical masks.
The study included 1,607 hospital staff working in high-risk wards at 14 secondary-level/tertiary-level hospitals in Hanoi, Vietnam. They were randomized to medical masks, cloth masks or a control group (usual practice, which included mask wearing). Participants used the assigned mask on every shift for 4 consecutive weeks. Cloth masks were washed with soap and water every day after finishing the shifts. Outcome measurements included clinical respiratory illness, influenza-like illness (ILI) and laboratory-confirmed respiratory virus infection.
The cloth mask group had the highest rate of all infections. In addition, cloth masks had statistically higher rates of ILI than the medical arm (RR 13) and the control arm. Particle penetration was 97% with cloth masks and 44% with medical masks.
The control group was not ideal, as investigators could not withhold use of masks. But the outcomes showed that cloth masks were inferior even to control arm (usual practice).
This study shows we should caution against use of cloth masks in health care settings, especially in high risk situations. It is important in the era of PPE shortage and COVID-19 that health care workers receive medical masks, not cloth masks.