The Centers for Disease Control and Prevention and other public health agencies recommend wearing masks to prevent transmission of COVID-19, but does the type of mask – cloth, surgical, or respirator – make a difference?
According to a new study published on September 8 in Royal Society Open Science, if only about half of the population had chosen to wear respirator-type masks since the start of the pandemic, COVID-19 would not have succeeded in establishing itself in the United States .
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“We were interested in determining effective ways to combat or alleviate the burden of a respiratory disease with pandemic potential during the very early stages, before pharmaceutical interventions, such as vaccines and antivirals became available,” said Gumel said. “Standard methods are generally based on quarantining those suspected of being at risk of the disease and isolating those showing symptoms. These measures have been shown to be largely ineffective in the face of highly contagious diseases, such as COVID-19. “
With COVID-19 ravaging the world, researchers thought to explore the potential impact of a widespread deployment of high-quality masks during the very early stages of the pandemic on the burden and trajectory of the pandemic.
Mixed messages have led to confusion and misunderstanding among the general public about the masks and their effectiveness.
“The public health messages around the masking were not clear initially, and the politicization of the masking, of course, didn’t help matters either,” Gumel said. “Since the start of the year, the message around masking has improved dramatically, with the only main issue being mask fatigue and the politicization effect which unfortunately still lingers in the minds of a significant proportion. Population.”
In the study, different types of masks are defined as well as their purpose and effectiveness. Cloth masks and surgical or procedural masks are considered loose face coverings and are designed to prevent the spread of disease from infected carriers to those around them, but not to protect the wearer from others. The effectiveness of sheet masks is difficult to determine due to their unregulated nature and variation in design and construction. Surgical masks are also designed to be loose, but are made from materials with a theoretical filtration efficiency of up to 85%. Due to their lack of tightness, the filtration efficiency in the real world is probably much lower.
Unlike fabric and surgical masks, most respirators are designed to fit tightly to the face and provide true respiratory protection, protecting the wearer from the respiratory hazards around them. Respirators are defined as properly fitted respiratory protective devices that meet or exceed the National Institute for Occupational Safety and Health (NIOSH) standard, and include N95, N99, N100, R95, P95, P99, and P100. Efficiency estimates for these filter mask respirators are close to 100% for charged biological particles such as respiratory aerosols.
Due to the highly protective nature of properly fitted respirators, healthcare workers have worn these devices to protect themselves from COVID-19 throughout the pandemic.
Previous mathematical modeling studies have focused on the role of tissue and surgical masks when adopted by a large majority of the population. What is not clear is what potential role respirator-type masks could play outside of healthcare and what level of use in the population would be needed to have a significant impact.
Researchers have formulated a basic mathematical model for the dynamics of COVID-19 transmission in a population where a certain proportion usually wear face masks. They considered four categories of face masks: cloth masks (with an estimated efficiency of 30%), improved cloth masks or ill-fitting surgical masks (with an estimated efficiency of 50%), well-fitted surgical masks ( with an estimated efficiency of 70%) and properly fitted respirators (with an estimated efficiency of 95%).
The first set of simulations assessed the impact of the early implementation of the mask use strategy in the United States. They simulated the scenario where only one of the four categories of masks is adopted in the community, and they used the reference values and parameters corresponding to the first wave of the pandemic. The results showed that the early implementation of the universal face mask use strategy, with 80% compliance, resulted in a dramatic reduction in the burden of the pandemic. If 80% of Americans wore respirators as of March 15, 2020 (four days after the World Health Organization declared COVID-19 a global pandemic), up to 84% of the nearly 128,000 deaths registered on June 30 would have been prevented.
The team performed additional simulations of the base model combining the impact of mask use with other non-pharmaceutical interventions (NPIs), such as social distancing, avoiding large gatherings, avoiding meals at home. interior in restaurants, etc. Since the model used COVID-19 data since the start of the outbreak in the United States (January 20, 2020 to mid-March 2021), the combined effects of other NPIs were already incorporated into the results. This means that the model calibration includes some benchmark level of other NPIs implemented in the community. The simulations showed that if individuals in the community chose to use only cloth masks, with an estimated effectiveness of 30%, COVID-19 would continue to spread.
In contrast, better quality masks required fewer people wearing them in order to effectively control the spread of the disease. If only 40% of Americans had worn highly effective breathing masks from the start of the epidemic, the pandemic could have been wiped out.
Additional simulations were conducted to assess the combined impact of using different types of face masks and other NPIs, using April 30, 2021 as a baseline for comparison. The results again showed that respirators are much more effective at reducing COVID-19 mortality than any other type of mask. The simulations also showed that the effectiveness of each type of mask improved when combined with an increase in the reference levels of other NPIs.
The study provided a range of plausible NPI-based scenarios to effectively control the spread of COVID-19 in the United States that would not necessarily require major economic disruption, such as the imposition of community lockdowns or shutdowns. large-scale businesses and schools. Much like in the previous two deadly global outbreaks of SARS and MERS, the study suggests that COVID-19 is controllable using basic public health interventions, using a strategy that prioritizes face masks. high quality.
“The ‘strike hard, strike early’ mantra, using high quality masks with high compliance, is the best way to suppress deadly pandemics – before vaccines and antivirals are available,” Gumel said. “Our study shows that if we had universally started masking ourselves early and using high-quality masks, COVID-19 would not have taken place in the United States – and the nearly 670,000 lives we have lost do have not had to die. It is in our collective interest to stockpile high quality masks, especially respirators, and deploy them massively in times of new contagious and deadly respiratory pandemics. “
The authors of the study are: Calistus N. Ngonghala, University of Florida; James R. Knitter, University of Arizona; Lucas Marinacci, Beth Israel Deaconess Medical Center and Harvard Medical School; Matthew H. Bonds, Harvard Medical School; Abba B. Gumel, Arizona State University and University of Pretoria, South Africa.
Abba Gumel acknowledges support, in part, from the Simons Foundation under award 585022 and from the National Science Foundation under grant DMS-2052363. Calistus N. Ngonghala acknowledges the support of the Simons Foundation under the award 627346.