Medical masks vs N95 respirators for preventing COVID-19 in healthcare workers: A systematic review and meta-analysis of randomized trials

Abstract

On March 11, 2020, Novel 2019 coronavirus disease (COVID-19) was declared a global pandemic and has steadily depleted healthcare organizations of essential personal protective equipment (PPE). Transmission of SARS-CoV-2 to healthcare workers is a serious threat with an early case series from Wuhan, China suggesting that 29% of hospitalized patients were healthcare workers. Although there is consensus on the use of N95 respirators for all aerosol-generating procedures to reduce transmission risk, guidelines have diverged in recommending N95 vs medical masks for non-aerosol-generating patient care. Evidence supporting non-inferiority of medical masks compared to N95 for routine care would allow preservation of diminishing N95 products, as well as provide reassurance that healthcare workers practicing such a protocol are safe. Authors searched multiple literature databases for English-language, randomized controlled trials (RCTs) from January 1, 2014 to March 9, 2020. This updated search was conducted by two independent reviewers and combined with the previous review completed on December 9, 2014. Eligible studies were RCTs, including cluster randomized trials, that compared medical masks with N95 respirators in healthcare workers at risk of exposure to acute respiratory illness. Included studies reported outcomes on laboratory confirmed viral infections (via PCR, serology or viral culture), laboratory-confirmed coronavirus infection, laboratory-confirmed influenza infection, influenza-like illness, clinical respiratory illness or work-place absenteeism. The primary outcome for the meta-analysis was reported laboratory confirmed viral infections. Data was extracted by a single reviewer and assessed by a second reviewer for quality control. Bias was assessed using a modified Cochrane risk of bias tool which evaluated selection bias, performance bias, detection bias, attrition bias and reporting bias. The grading of recommendations, assessment, development and evaluation (GRADE) approach was used to evaluate for certainty of the evidence. Data analysis included pooled odds ratios (ORs) with 95% confidence intervals (CIs) and evaluation of data heterogeneity. Authors used adjusted meta-analysis to account for the clustered nature of the included RCTs. Of 389 screened titles and abstracts and 12 full texts, the systematic review yielded 1 additional RCT (n = 5180). The combination of this study with the three trials from a 2016 systematic review resulted in a total of four randomized controlled trials examining medical masks (n = 3957) vs N95 respirators (n = 4779) in healthcare workers treating patients with acute respiratory illness. Although PCR testing for viruses in the Coronavidiae family was completed in all studies, data specifically on coronavirus was limited to a single study. Additionally, only a single study reported workplace absenteeism. Comparison of medical masks vs N95 respirators for laboratory-confirmed viral respiratory infection yield a pooled OR 1.06 (95% CI 0.90-1.25), I2 = 0%. Results for laboratory-confirmed influenza infection and influenza-like illness were OR 0.94 (95% CI 0.73-1.20), I2 = 0% and OR 1.31 (95% CI 0.94-1.85), I2 = 5%, respectively. In the study which specifically reported coronavirus, there were infections rates of 4.3% (9/212) and 5.7% (12/210) in the medical mask vs N95 respirator groups, respectively (p = 0.49). Work-related absenteeism was 19.8% and 18.6% for medical masks vs N95 respirators, respectively (p = 0.75). Although risk of selection bias, attrition bias and reporting bias were low amongst all RCTs, the risk of detection bias was high for non-laboratory confirmed outcomes. There was also high risk of performance bias given the absence of participant blinding. Additionally, evidence was low for laboratory-confirmed outcomes and very low for non-laboratory confirmed outcomes. The authors state that the current evidence supporting either inferiority or non-inferiority of medical masks to N95 respirators for routine care (i.e., non-aerosol generating procedures) is insufficient. Additionally, there are no quality studies specifically evaluating medical masks vs N95 respirators in the treatment of COVID-19. A limitation of this systematic review and meta-analysis includes that only a single trial examined coronavirus infection individually and therefore, generalizability to SARS-CoV-2 is unclear. The fact that the meta-analysis was performed on aggregate data is an additional limitation. Accounting for cluster randomization should be viewed as a strength which was not done in the previous meta-analysis. Due to concern for N95 respirator availability with the current pandemic, use of medical masks should be considered. However, certainty of evidence is low and additional studies are needed. Comment: Healthcare workers have been forced into an area of uncertainty with regard to appropriate PPE due to conflicting and ever-changing guidelines. Although data is limited, hopefully they can find solace in the current literature that at least suggests medical masks may be sufficient for routine patient care. Funding for further research should be a priority given the high rates of transmission to healthcare workers with the current COVID-19 pandemic. Additionally, such research will hopefully further prepare the healthcare system for future pandemics.