The Efficacy of Facemasks in the Prevention of COVID-19: A Systematic Review

Abstract

Facemasks have become a symbol of disease prevention in the context of COVID-19; yet, there still exists a paucity of collected scientific evidence surrounding their epidemiological efficacy in the prevention of SARS-CoV-2 transmission. This systematic review sought to analyze the efficacy of facemasks, regardless of type, on the prevention of SARS-CoV-2 transmission in both healthcare and community settings.

The initial review yielded 1732 studies, which were reviewed by three study team members. Sixty-one full text studies were found to meet entry criteria, and 13 studies yielded data that was used in the final analysis.

In all, 243 subjects were infected with COVID-19, of whom 97 had been wearing masks and 146 had not. The probability of getting COVID-19 for mask wearers was 7% (97/1463, p=0.002), for non-mask wearers, probability was 52% (158/303, p=0.94). The Relative Risk of getting COVID-19 for mask wearers was 0.13 (95% CI: 0.10-0.16).

Based on these results, we determined that across healthcare and community settings, those who wore masks were less likely to contact COVID-19. Future investigations are warranted as more information becomes available.

Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a member of the Coronaviridae family, is the causative agent of COVID-19. It is the seventh known coronavirus to infect humans: others include SARS-CoV-1, the causative agent of SARS, MERS-CoV, the causative agent of MERS, as well as HCoV-229E, -NL63, -OC43, and -HKU1 which are endemic human coronaviruses and are among the causative agents of the common cold.1 SARS-CoV-2 is reported to have emerged from the Huanan South China Seafood Market in Wuhan City, Hubei Province, China in late 2019. The virus quickly spread throughout the country, and then across the world. In response, the WHO declared a global health emergency on January 31, 2020, and later a pandemic on March 11, 2020.2

Despite the swiftness with which the virus spread, responses to the pandemic varied greatly by country. Throughout the course of the pandemic, the use of facemasks in prevention of the transmission of SARS-CoV-2 has remained one of the most contentious topics. Many East Asian countries, who had experience with the SARS epidemic in the early 2000s were quick to recommend that their citizens wear facemasks in public. Many of these countries had a public which remembered the SARS epidemic and had experience using facemasks in the prevention of viral transmission.3 The Chinese government issued guidelines recommending the personal use of facemasks on January 31, 2020.4 The government of Hong Kong recommended that its citizens use facemasks as early as January 24, 2020.5 In contrast to this, the CDC did not recommend that U.S. citizens wear facemasks until early April6, and the WHO did not officially recommend that members of the public wear masks until June 5, 2020.7

At the beginning of the pandemic, disruption of supply chains and increased use of personal protective equipment (PPE) caused concerns of widespread shortages, including facemasks.8 These concerns may have influenced some of the initial recommendations by the CDC and WHO, as officials feared that widespread use of facemasks might exacerbate PPE shortages, thus limiting supplies for healthcare workers treating COVID-19 in hospital settings. These initial conflicting guidelines by government and international bodies became a source of confusion in the general public, and contributed to the politicization of facemask use in places like the U.S.9

Despite disparity in facemask use by country early in the pandemic, many public policy decisions were made in the absence of guidance from peer-reviewed scientific sources. Even though the facemask has become a symbol of disease prevention in the context of COVID-19, there still exists a paucity of collected scientific evidence surrounding the epidemiological efficacy of facemasks in the prevention of SARS-CoV-2 transmission. This systematic review sought to analyze the efficacy of facemasks, regardless of type, on the prevention of SARS-CoV-2 transmission in both healthcare and community settings. It was hypothesized that wearing a facemask would be associated with lower rates of COVID-19.

Methods

A systematic review was conducted to identify relevant studies. A medical librarian conducted a literature search utilizing Pubmed, Web of Science, Embase and Cochrane library from April 2020 to August 2020. Citations were deduplicated using Covidence.org. Only English language articles were retrieved, and conference proceedings were omitted. Results were reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. The following broad strategy was utilized: Masks: Mask[text word(tw)] OR masks[tw] OR facemask[tw] OR facemasks[tw] OR “face mask”[tw] OR “face masks”[tw] OR “face covering”[tw] OR “face coverings”[tw] OR “masks[medical subject headings (mesh)].”COVID-19: “COVID-19”[Supplementary Concept] OR “severe acute respiratory syndrome coronavirus 2”[Supplementary Concept] OR “Coronavirus Infections”[Mesh] OR “COVID-19”[tw] OR “covid19”[tw] OR “covid2019”[tw] OR “ncov2019”[tw] OR “ncov-2019”[tw] OR “2019-nCoV”[tw] OR “2019nCoV”[tw] OR “nCoV”[tw] OR “2019 ncov”[tw] OR “2019nCoV”[tw] OR “COV 2”[tw] OR “CoV2”[tw] OR “SARS-CoV-2”[tw] OR “SARSCoV2”[tw] OR “sars cov 2”[tw] OR “sars coronavirus 2”[tw] OR “HCoV-19”[tw] OR “novel coronavirus”[tw] or “covid”[tw] OR “coronavirus disease 2019”[tw] OR 2019 “novel coronavirus disease”[tw] OR “covid-19 pandemic”[tw] OR “2019 novel coronavirus infection”[tw] OR “SARS-CoV-2 infection”[tw] or “2019-nCoV infection”[tw] or “COVID-19 virus disease”[tw] or “2019 novel coronavirus infection”[tw] or “2019-nCoV disease”[tw].

The initial review yielded 1732 studies, which were reviewed by three study team members. Sixty-one full text studies were found to meet the criteria, and 13 studies were used in the final analysis. (Figure 1) Frequencies, relative risk, confidence intervals and t-tests were calculated where appropriate, to measure differences between groups who reported wearing masks vs. not wearing masks for the overall study group, as well as health care, and community settings.

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