July 8, 2020
Physical Barriers for Prevention Amidst a Pandemic: The Roles of Distancing, Masks, and Eye Protection
Reviewed by Kelly Cawcutt, M.D., MS
As we continue forward in a global pandemic of unprecedented proportions, prevention of continued transmission of SARS-CoV-2 remains critically important. There has been ongoing debate regarding the highest risk factors for transmission, including the risk of potential aerosolized virus versus primary droplet spread. The appropriate levels of personal protective equipment (PPE) for both frontline health care workers and the public have also remained controversial.
In an attempt to answer this question, Chu et al. recently published a systematic review and meta-analysis in The Lancet assessing physical distancing, face masks of varying types, and eye protection within health care and non-health care settings to determine if there is evidence to support ongoing recommendations for their use.
The review included published research related to SARS, MERS, and COVID-19. Of note, all the studies were observational. The results demonstrated that transmission of infection decreased with physical distancing of at least 1 meter (adjusted odds ratio [OR] 0.18; 95% confidence interval [CI] 0.09-0.38) with a risk reduction of approximately 10% and increasing protection if the distance was extended to 2 meters or greater. Additionally, the use of face masks in all settings was associated with decreased transmission of infection (adjusted OR 0.15, 95% CI 0.07-0.34) with a risk reduction of approximately 14%. There were some potential differences in mask type, with decreased transmission with respirators (N95) as compared to surgical or cloth masks. Finally, eye protection (including goggles and faceshields) also demonstrated decreased risk of transmissions with use (adjusted OR 0.22; 95% CI 0.12 -0.39) with a risk reduction of approximately 10%.
This study provides early evidence of the efficacy of continued PPE use to prevent transmission of COVID-19, both in the community and in the health care setting, including continued physical distancing, face mask use, and eye protection. It should be noted that the impact of face mask and eye protection use was not adjusted for the duration of time spent with an actively infected person nor the impact of physical distancing in the absence of the masks or eye protection. The variation of impact among different types of masks, including N95s, is difficult, at best, to interpret due to the lack of randomized controlled trials, lack of information on aerosol-generating procedures within studies, and potential variations both in mask quality, appropriate fit of masks, donning and doffing, and hand hygiene.
Further research is clearly needed to optimize PPE utilization in the setting of existing shortages faced during this pandemic and for ongoing public health and infection control policy on health care-based PPE recommendations.