title: A cluster randomised trial of cloth masks compared with medical masks in healthcare workers.
abstract: OBJECTIVE
  The aim of this study was to compare the efficacy of cloth masks to medical masks in hospital healthcare workers (HCWs). The null hypothesis is that there is no difference between medical masks and cloth masks.
  
  
  METHODS
  14 secondary-level/tertiary-level hospitals in Hanoi, Vietnam.
  
  
  METHODS
  1607 hospital HCWs aged ≥18 years working full-time in selected high-risk wards.
  
  
  METHODS
  Hospital wards were randomised to: medical masks, cloth masks or a control group (usual practice, which included mask wearing). Participants used the mask on every shift for 4 consecutive weeks.
  
  
  METHODS
  Clinical respiratory illness (CRI), influenza-like illness (ILI) and laboratory-confirmed respiratory virus infection.
  
  
  RESULTS
  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%.
  
  
  CONCLUSIONS
  This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally. However, as a precautionary measure, cloth masks should not be recommended for HCWs, particularly in high-risk situations, and guidelines need to be updated.
  
  
  BACKGROUND
  Australian New Zealand Clinical Trials Registry: ACTRN12610000887077.
authors.affiliation: Faculty of Medicine, School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia.
authors.forename: C Raina
authors.initials: CR
authors.lastname: MacIntyre
authors.affiliation: Faculty of Medicine, School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia.
authors.forename: Holly
authors.initials: H
authors.lastname: Seale
authors.affiliation: National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.
authors.forename: Tham Chi
authors.initials: TC
authors.lastname: Dung
authors.affiliation: National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.
authors.forename: Nguyen Tran
authors.initials: NT
authors.lastname: Hien
authors.affiliation: National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.
authors.forename: Phan Thi
authors.initials: PT
authors.lastname: Nga
authors.affiliation: Faculty of Medicine, School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia.
authors.forename: Abrar Ahmad
authors.initials: AA
authors.lastname: Chughtai
authors.affiliation: Faculty of Medicine, School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia.
authors.forename: Bayzidur
authors.initials: B
authors.lastname: Rahman
authors.affiliation: Institute for Clinical Pathology and Medical Research, Westmead Hospital and University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Dominic E
authors.initials: DE
authors.lastname: Dwyer
authors.affiliation: Beijing Centers for Disease Control and Prevention, Beijing, China.
authors.forename: Quanyi
authors.initials: Q
authors.lastname: Wang
mesh_terms: D000328:Adult; D000368:Aged; D001315:Australia; D016000:Cluster Analysis; D005260:Female; D006801:Humans; D017053:Infection Control / Q000295:instrumentation*; D007251:Influenza, Human / Q000517:prevention & control; D008297:Male; D008397:Masks / Q000592:standards*; D008875:Middle Aged; D009520:New Zealand; D016273:Occupational Exposure / Q000517:prevention & control* / Q000706:statistics & numerical data; D009786:Occupational Health Services / Q000379:methods*; D010564:Personnel, Hospital / Q000706:statistics & numerical data*; D012367:RNA, Viral / Q000302:isolation & purification; D012134:Respiratory Protective Devices / Q000592:standards*; D012141:Respiratory Tract Infections / Q000517:prevention & control* / Q000821:virology
chemical_list: D012367:RNA, Viral
keywords: Cloth mask; Influenza