Urgency and uncertainty: covid-19, face masks, and evidence informed policy

Even healthcare workers can struggle with appropriate mask use2; cloth masks are less effective than medical masks3; and poor use reduces effectiveness and poses an infection risk.4 Second, encouraging uptake of face masks might lead to “risk compensation”: reduced compliance with other measures.56 Third, there are potential societal consequences, such as a rush to obtain equipment intended for use by healthcare workers should cloth masks prove ineffective or using mask wearing to justify unsafe workplaces or commuting conditions.7 Finally, the indirect consequences of an intervention in a complex system are inherently difficult to predict. A lay summary of the evidence for face masks authored by Greenhalgh and Howard declares simply that “the science says yes” to masks.11 Alongside Greenhalgh’s analysis piece,1 the principal source for this claim is an unreviewed literature review with very limited methods, susceptible to bias.12 Such unequivocal advocacy for face masks risks overstepping current knowledge and promoting policy change based more on eminence than evidence. King’s College London News Centre. 2020. https://www.kcl.ac.uk/news/why-reassuring-the-public-may-not-be-the-best-way-to-end-lockdown 10 Reed JE Howe C Doyle C Bell D. Simple rules for evidence translation in complex systems: a qualitative study.