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Regular medical masks might provide protection similar to that of N95 respirators in preventing SARS-CoV-2 infection among healthcare workers, according to the first randomized trial that tested the two types of masks head to head in the COVID-19 era.
Owing to limitations in the study, however, the authors were only formally able to conclude that healthcare workers who wore medical masks while treating COVID-19 patients were not twice as likely to contract the virus as workers wearing N95 respirators.
“Nonetheless, this trial provides the best evidence to date on comparative effectiveness of mask types in preventing SARS-CoV-2 infection in health care workers providing routine patient care,” writes Roger Chou, MD, in an editorial published with the study.
In summarizing, Chou said that “the results indicate that medical masks may be similar to N95 respirators in Omicron-era settings with high COVID-19” rates, but the researchers set a low bar for establishing whether one is more effective than the other.
“Therefore, the results are not definitive,” Chou writes.
In the study, published Tuesday in Annals of Internal Medicine, the authors evaluated 1009 healthcare workers in Canada, Israel, Pakistan, and Egypt who had not been vaccinated against SARS-CoV-2 and had not previously been infected by the virus. Participants were randomly assigned to wear either a medical mask or an N95 respirator for 10 consecutive weeks. The study period was from May 2020 to March 2022.
Reverse transcriptase polymerase chain reaction tests confirmed that COVID occurred in 52 of 497 (10.46%) participants in the medical mask group, vs 47 of 507 (9.27%) in the N95 respirator group (hazard ratio [HR], 1.14; 95% CI, 0.77 – 1.69).
The World Health Organization recommends medical masks (sometimes called surgical masks) for routine care, while the Centers for Disease Control and Prevention recommends that N95s be used while caring for COVID-19 patients. Prior to the pandemic, research showed that N95s and medical masks carried similar risks while caring for patients with influenzalike illnesses.
Chou said decision-makers should keep in mind the uncertainty of whether one mask type is more effective than the other and should take worker preferences, N95 respirator availability, and resource constraints into consideration.