More evidence mask wearing works to contain COVID-19 spread

By Dr. Ananya Mandal, MDAug 26 2020

A team of American researchers has looked at the effects of wearing face masks and the prevention of the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) between individuals. As of today, over 5.8 million people in the USA have been infected with the virus. This new study titled, “Mask Wearing and Control of SARS-CoV-2 Transmission in the United States,” is published on the preprint server medRxiv*.

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This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources

What was the study about?

As a response to the COVID-19 pandemic wearing face covers such as cloth masks or surgical masks has been recommended across the nation. Several studies have shown that masks can prevent the spread of respiratory infections. However, there is still a raging debate regarding the general public wearing face masks. The authors wrote, “In the absence of a vaccine or curative therapy, governments in the United States and worldwide have adopted numerous approaches to curb the virus’s continued transmission.” They outlined the non-pharmaceutical measures of transmission prevention, such as the use of face masks and respirators.

Studies have shown that N95 respirators are one of the best methods to prevent viral respiratory transmission. However,  there is a shortage of these masks because they are preferentially allocated to high-risk, front-line medical personnel. For the general population, the recommendation is cloth face coverings and surgical masks. After the initial spread of the infection in the USA, many local and state jurisdictions made it compulsory for the general public to use these face masks in certain settings. The masks are said to provide a mechanical barrier that could absorb the virus-laden droplets which are expelled by the user. Thus these masks can prevent the spread of infection from the user rather than protect them from infection, write the researches. The team wrote, “face masks are advocated as a source of collective benefit, akin to herd immunity with vaccination, which is most successful with high levels of adoption.”

This study was conducted to investigate the actual association between “self-reported mask-wearing, social distancing and community SARS-CoV-2 transmission in the United States”. The authors also wanted to see the adherence to mandates issued by the government regarding wearing face masks.

What was done?

A series of cross-sectional surveys were conducted between 3^rd June and 31^st July 2020 using a web platform. The participants on the survey were asked about their likelihood of wearing a face mask when they are with family and friends, and when they visit the grocery stores.

A total of 378,207 responses were gathered. These were all collated by week and the states from where they were obtained. Other factors were also taken into consideration. These included “instantaneous reproductive number (Rt)” which transmission of the infection, social distancing measures, and the demographic features of the respondents. Multivariate logistic regression models were used to find an association between mask-wearing and community transmission control (depicted by Rt < 1) for every state and each week.

The team also looked at the level of adherence to the mandates regarding mask wearing for 12 states, two weeks before and after such mandates were imposed.

What was found?

The main findings of the study were

• Despite variations across regions and communities, there was a definite increase in mask wearing among the American population
• Using statistical modeling the team found that a 10 percent increase in wearing masks was linked to 3.53 odds of transmission control (depicted by Rt <1).
• Those communities that wore masks more frequently and practiced social distancing had a higher probability of controlling the pandemic and its spread
• Accounting for all other factors, mask-wearing, and social distancing held true in their positive association with transmission prevention
• With time there has been a positive trend in mask wearing they noted, but no significant change was seen following the mandates.

Conclusions and implications

The authors of the study concluded that extensive use of face masks along with social distancing could increase the odds of SARS-CoV-2 transmission control. They wrote, “A 10% increase in mask-wearing was associated with an over three-fold increase in odds of transmission control.” They also wrote, “Mask wearing rose separately from government mask mandates, suggesting supplemental public health interventions are needed to maximize mask adoption and disrupt the spread of SARS-CoV-2”. They wrote that since the social distancing measures are being relaxed with time, public health interventions to increase mask-wearing become more vital. The authors concluded, “Given mixed evidence on the effect of mask mandates, but a strengthening body of evidence on the effect of masks, policymakers should consider innovative strategies for evaluating and increasing mask usage to help control the epidemic.”

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources