Does Wearing A Mask Prevent the Spread of COVID-19?

by | Jul 14, 2020 | 2020, COVID-19, Lung Health

Written by Joyce Smith, BS. This study concludes that mandating public use of face masks is associated with a reduction in the COVID-19 pandemic.

immune -health - COVID-19 - maskGovernments worldwide, by mandating closures of schools and non-essential businesses and sheltering-in-place, are battling the spread of the highly contagious COVID-19 pandemic. One of the most contentious debates regarding COVID-19 is that of wearing a face mask or an alternative but appropriate face covering when in public settings 1. Driving the debate is the fact that for some time we had limited knowledge as to whether widespread mask-wearing could positively effect COVID-19’s spread 2,3. Substantial evidence of asymptomatic transmission in small geographical areas now exists; however, there is not yet direct evidence that mask-wearing prevents or reduces transmission at a population level. Varying criteria for the reopening of economies and the easing of social distancing requirements, coupled with the conflicting messaging regarding public use of surgical masks and N95 respirators, has contributed greatly to loss of confidence in leadership. Therefore, scientific evidence addressing the importance of wearing masks is important for governments and public health authorities alike, but the evidence is particularly important for public education.

Researchers from the department of public health, University of Iowa, 4 using a statistical method called an event study, found a reduction in COVID-19 spread by examining daily changes in county-level COVID-19 growth rates in 15 states and the District of Columbia, all of which mandated the use of masks. Researchers chose the time period for estimating the effects of mandating face masks and face coverings as “one to five days before signing the order”. They then measured the changes in the effects of the mandates over increments of five days (1–5 days, 6–10 days, 11–15 days, 16–20 days, and 21+ days). The reductions in COVID-19 spread, calculated in percentage points, during the days immediately after the executive orders were as follows:

  • 1-5 days: 0.9 percentage points.
  • 6-10 days: 1.1 percentage points.
  • 11-15 days: 1.4 percentage points.
  • 16-20 days: 1.7 percentage points.
  • 21-or-more days: 2.0 percentage points.

Analysis suggested that by May 22nd, masks may have prevented 230,000 to 450,000 COVID-19 cases in 15 states, including Connecticut and the District of Columbia. (These states adopted mask mandates early in the pandemic for both the general public and employees). To assess the effects of face masks and covers for employees only, they estimated another event-study model that focused on the 20 states that mandated face masks and coverings for employees only and the 15 states without an employee mandate. (This analysis excluded the 15 states plus the District of Columbia that had both public and employee face cover mandates).

The estimated reductions in COVID-19 spread are significant and represent nearly 16–19% of the total effects of other social distancing measures (school closures, bans on large gatherings, shelter-in-place orders, and closures of restaurants, bars and entertainment venues) during the same time frame 5.

The researchers suggest viewing the number of potential averted COVID-19 cases, up to 450,000, with caution since they were unable to measure compliance with, or enforcement of, the mask mandate in each state. It should also be noted that wearing a mask is not a substitute for social distancing measures since its effectiveness depends in part on how well communities comply with social distancing. With the potential for a second resurgence of COVID-19 in the coming fall and winter 6, particularly as countries worldwide relax their policies, wearing a mask in public may be an important measure for mitigating COVID-19 spread.

Source: Lyu, Wei, and George L. Wehby. “Community Use Of Face Masks And COVID-19: Evidence From A Natural Experiment Of State Mandates In The US: Study examines impact on COVID-19 growth rates associated with state government mandates requiring face mask use in public.” Health Affairs (2020): 10-1377.

 Copyright Project HOPE—The People-to-People Health Foundation, Inc.

Posted July 14, 2020.

Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from  the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.

References:

  1. Feng S, Shen C, Xia N, Song W, Fan M, Cowling BJ. Rational use of face masks in the COVID-19 pandemic. The Lancet Respiratory medicine. 2020;8(5):434-436.
  2. Furukawa NW, Brooks JT, Sobel J. Evidence Supporting Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 While Presymptomatic or Asymptomatic. Emerg Infect Dis. 2020;26(7).
  3. Mizumoto K, Kagaya K, Zarebski A, Chowell G. Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020. Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin. 2020;25(10).
  4. Lyu W, Wehby GL. Community Use Of Face Masks And COVID-19: Evidence From A Natural Experiment Of State Mandates In The US. Health Aff (Millwood). 2020:101377hlthaff202000818.
  5. Courtemanche C, Garuccio J, Le A, Pinkston J, Yelowitz A. Strong Social Distancing Measures In The United States Reduced The COVID-19 Growth Rate. Health Aff (Millwood). 2020;39(7):1237-1246.
  6. Sun L. CDC director warns second wave of coronavirus is likely to be even more devastating. 2020; https://www.washingtonpost.com/health/2020/04/21/coronavirus-secondwave-cdcdirector/. Accessed June 8, 2020.