Masks During Pandemics Caused by Respiratory Pathogens—Evidence and Implications for Action

JAMA More than 3 years after the COVID-19 pandemic began, the use of face masks in the community remains controversial. Vaccination, treatment, population immunity, and other developments have enabled a return to a semblance of prepandemic life, but disagreement about what the evidence shows about masks—and the implications for their use—persists. SARS-CoV-2 is still a disruptive and deadly presence, and future epidemics or pandemics caused by pathogens spread by the respiratory route are a near certainty.¹ Failure to understand the evidence on the role of masks in preventing the spread of SARS-CoV-2 could undermine our ability to respond to epidemics and pandemics caused by respiratory pathogens.

In early 2020, when SARS-CoV-2 was spreading globally and the World Health Organization declared a Public Health Emergency of International Concern, there were neither vaccines against nor treatments for COVID-19. Furthermore, we lacked understanding of the virus’s routes of transmission, extent of presymptomatic and asymptomatic spread, and degree of transmissibility. As a result, prevention and control strategies were based on what was known about transmission of other respiratory pathogens, especially influenza viruses and previously characterized human betacoronaviruses, such as those that cause severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and the common cold.^2–4 Public health officials needed to consider that available evidence came from studies on specific types of masks (particularly N95 respirators vs surgical masks), that there was variation in the aims of masking interventions (ie, wearer protection vs source control), and that epidemiologic and behavioral differences between study settings (especially in health care settings vs the community) might influence apparent mask effectiveness.

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