Universal masking for COVID-19: evidence, ethics and recommendations

• Published in: BMJ global health 2020-05, Vol.5 (5), p.e002819
• Main Author: Chan, Tak Kwong
• Format: Article
• Language: English
• Subjects: Betacoronavirus; Bias; Commentary; Coronavirus Infections; Coronaviruses; COVID-19; Disease control; Disease transmission; Dormitories; Global health; Health administration; health policies and all other topics; Health promotion; Households; Humans; Hygiene; Influenza; Intervention; Laboratories; Masks; Medical ethics; Medical personnel; Observational studies; Pandemics; Personal hygiene; Pneumonia, Viral; Protective equipment; Public awareness; Public health; SARS-CoV-2; Social distancing; Systematic review
• ISSN: 2059-7908; 2059-7908
• DOI: 10.1136/bmjgh-2020-002819

Current best available evidence should guide urgent policy While public health decisions should be evidence-based, drawing on randomised controlled trials (RCT) as an important source of information, the methodological challenges of evaluating large-scale public health interventions need to be recognised.12 When there is logistic difficulty in conducting an RCT, evidence from other data sources can provide valid support for an urgent public health action.13 The mechanistic effects of handwashing and wearing a face mask have been demonstrated, thus offering some scientific basis for their benefits in terms of disease control.4 5 A recently published article shows turbulent gas cloud can prolong the life of pathogen-bearing droplets and allow them to travel a longer distance. Some experts suggested that while there is a perception that wearing a face mask may help, there is little evidence of any benefit outside the clinical setting.15 In a recent meta-analysis, six RCTs were identified reporting the effect of wearing a face mask with enhanced hand hygiene in reducing laboratory-confirmed influenza in the community.2 Although none of them supported a significant protective effect,2 all the authors acknowledged that their studies may have underestimated the effect of the intervention (see table 1 for their limitations).16–21 Their results also may not be generalisable to the universal use of face masks in the community during an actual pandemic which should result in heightened level of public awareness and community efforts. Furthermore, an absence of evidence (from RCTs in this instance) should be distinguished from evidence of absence.22 A previous systematic review identified two case controlled observational studies to assess the effectiveness of wearing a face mask in the community.23–25 Subsequent to that systematic review, one further relevant observational study was published.26 All these three observational studies concurred with each other, showing a significant protective effect of face masks in the community, although their findings may be limited by misclassification and reporting bias (see table 2 for details). While there are occasions when systematic review (of RCTs) is the ideal approach to answering specific forms of questions, the absence of thoughtful, interpretive critical reflection can render such products hollow, misleading and potentially harmful’.27 Table 2 Summary of evidence—observational studies for the effectiveness of face mask