Physical Distancing, Face Masks, and Eye Protection to Prevent COVID-19
- Physical distancing ≥1 m, face masks, and eye protection are associated with a 75-85% relative reduction in the risk of infection.
- N95 or similar respirators appear to be more effective in reducing the risk of infection compared to other masks, especially in health care settings.
- Findings are derived from observational studies, and did not differ according to virus (COVID-19, SARS, or MERS).
How effective are physical distancing, face masks, and eye protection to prevent person-to-person transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)?
The authors performed a systematic review, which included 172 studies from across the world, among which 44 comparative studies were included in a meta-analysis. They included studies of any design and in any setting that included patients with World Health Organization (WHO)-defined confirmed or probable coronavirus disease 2019 (COVID-19), severe acute respiratory syndrome (SARS), or Middle East respiratory syndrome (MERS), and people in close contact with them, comparing distances between people and COVID-19 infected patients of ≥1 m (≥3.3 feet) with smaller distances, with or without a face mask on the patient, or with or without a face mask, eye protection, or both on the exposed individual. No randomized trial was identified in the search. The primary outcome of interest was risk of transmission of WHO-defined confirmed or probable COVID-19, SARS, or MERS to people in health care or non–health care settings.
Proximity was strongly associated with the risk of infection, with absolute risk (AR) of 12.8% with shorter distance versus 2.6% with further distance. The association was larger with increasing distance (2.02 change in relative risk per m, 95% confidence interval [CI], 1.08-3.76; p for interaction = 0.041). The association was seen irrespective of causative virus, health care setting versus non–health care setting, and by type of face mask. Use of N95 or face masks by those exposed to infected individuals was associated with a large reduction in risk of infection (AR 3.1% with face mask vs. 17.4% with no face mask), with stronger associations in health care settings compared with non–health care settings. Protection from infection was more pronounced with N95 or similar respirators (adjusted odds ratio, 0.04; 95% CI, 0.004-0.30) compared with other masks. Eye protection was associated with lower risk of infection (AR, 5.5% with eye protection vs. 16.0% with no eye protection). Most stakeholders found physical distancing and use of face masks and eye protection acceptable, feasible, and reassuring. Challenges included frequent discomfort, high resource use linked with potentially decreased equity, less clear communication, and perceived reduced empathy of care providers.
Physical distancing of ≥1 m, face masks, and eye wear are associated with a lower risk of infection from SARS, MERS, or COVID-19.
Conducting randomized trials to test the effectiveness of physical distancing in reducing the risk of infection is at the least a herculean task, if not impossible. Despite the limitations of the studies included in this systematic review, the authors have used various analytical approaches to the data, with results that support the main conclusions. As such, this study represents the best observational evidence supporting physical distancing and the use of protective equipment as strategies to reduce the risk of infection, whether in the health care or public setting. The effect size associated with these measures was significant, and applies to COVID-19, SARS, MERS, and likely to the inevitable future pandemic. While these data do not absolve the need for randomized trials, they are invaluable in improving modeling accuracy and informing health policy.
Clinical Topics: Prevention
Keywords: Coronavirus, COVID-19, Eye Protective Devices, Health Resources, Masks, Personal Protective Equipment, Primary Prevention, Risk, SARS Virus, Severe Acute Respiratory Syndrome, severe acute respiratory syndrome coronavirus 2, Social Distance
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