Medical Masks as Effective as N95 Respirators. Credit | iStock
Medical Masks as Effective as N95 Respirators. Credit | iStock

Are Medical Masks as Effective as N95 Respirators? Experts Warn Against Jumping to Conclusions!

United States: A recent investigation published in the Annals of Internal Medicine posits that medical masks may provide akin effectiveness to N95 respirators in safeguarding healthcare workers (HCWs) who come into contact with COVID-19 patients in specific scenarios. Nevertheless, experts advise against hasty conclusions drawn from these findings.

The World Health Organization (WHO) advocates for the continuous utilization of either medical masks or N95s when attending to COVID-19 patients, whereas the US Centers for Disease Control and Prevention (CDC) advocates for the use of N95s, according to

Substantial disparities among countries

This randomized trial, coordinated by McMaster University researchers in Canada, tracks the COVID-19 illness among 1009 healthcare personnel directly caring for patients with COVID-19 across 29 hospitals from Canada, Israel, Pakistan, and Egypt from May 4, 2020, to March 29, 2022. This will become the first such peer-reviewed randomized and controlled clinical trial that will focus on the masks’ effectiveness among healthcare workers in the prevention of COVID.

The study participants were randomly sorted as wearing a medical face mask or a fit-tested N95 FFR for ten weeks. The fit-testing method was not described in the study design. Confirmation of the COVID-19 infection was a case of a reverse transcriptase polymerase chain reaction (RT PCR) in 52 out of 497 (10.46%) HCWs in the group of medical masks, and compared with this, in the group of N95 masks, there was 47 out of 507 (9.27%).

 Medical Masks as Effective as N95 Respirators. Credit | Jennifer Swanson/NPR
Medical Masks as Effective as N95 Respirators. Credit | Jennifer Swanson/NPR

A subgroup analysis revealed that 8 out of 131 (6.11%) HCWs in the medical mask group and 3 out of 135 (2.22%) in the N95 group were infected in Canada (HR, 2.83; 95% CI, 0.75 to 10.72), while 6 out of 17 (35.29%) versus 4 out of 17 (23.53%) were infected in Israel (HR, 1.54; 95% CI, 0.43 to 5.49), 3 out of 92 (3.26%) versus 2 out of 94 (2.13%) in Pakistan (HR, 1.50; 95% CI, 0.25 to 8.98), and 35 out of 257 (13.62%) versus 38 out of 261 (14.56%) in Egypt (HR, 0.95; 95% CI, 0.60 to 1.50).

The authors cautioned that HCWs might have contracted the infection outside the hospital environment, and as such, the findings might not be applicable universally due to variations in treatment effects. Moreover, the wide confidence intervals signify a substantial level of uncertainty, discrepancies in self-reported adherence and initial SARS-CoV-2 antibody status, as well as variations among countries in vaccination rates and prevalent circulating variants, may have influenced the outcomes, reported.

“In the case of healthcare workers who delivered standard care to COVID-19 patients, the overall estimations preclude a twofold increase in the hazard of RT-PCR–confirmed COVID-19 for medical masks when juxtaposed with HRs of RT-PCR–confirmed COVID-19 for N95 respirators,” they concluded.

“The surgical masks did not exhibit statistical inferiority to N95s in preventing COVID-19 infections in healthcare providers attending to COVID-19 patients,” remarked lead author Mark Loeb, MD, in a McMaster press release dispatched to journalists. Loeb conveyed to CIDRAP News that his clinical obligations precluded the availability of time for an interview regarding the study’s findings.

However, Michael Osterholm, Ph.D., MPH, director of the Center for Infectious Disease Research and Policy at the University of Minnesota and publisher of CIDRAP News, advocated for a shift in scientific inquiry away from medical masks, which have already been established as less effective compared to N95s. “We do not require another inadequately formulated and conducted study on this matter,” he asserted.

 Medical Masks as Effective as N95 Respirators. Credit | Alberto Mihai/
Medical Masks as Effective as N95 Respirators. Credit | Alberto Mihai/

Osterholm criticized the WHO’s recommendation for HCWs to utilize either masks or N95s during COVID-19 patient care, branding it as “public health malpractice.”

“I am convinced that in the future, people will look back on this and question, ‘How could they have been aware of this information and not taken greater measures to safeguard us?'” he added.

The organization was slow to acknowledge that SARS-CoV-2 transmits through aerosols instead of droplets, a lapse that WHO Chief Scientist Soumya Swaminathan, MBBS, MD, who is stepping down from her position, now acknowledges as her primary regret.

Disputing the conventional belief in mask effectiveness

Expounding on the authors’ reservations, Raina MacIntyre, MBBS, Ph.D., a prominent researcher and epidemiologist at the University of New South Wales in Sydney, who was not involved in the study, contended that the Annals study was inconclusive and failed to substantiate its conclusion due to flaws in its methodology, as reported.

“It illustrates a general inclination towards N95s outperforming surgical masks at all sites except Egypt, noting that both study groups utilized an N95 respirator for aerosol-generating procedures, and the intervention was solely evaluated during periods of care unrelated to such procedures,” she asserted.

MacIntyre highlighted that HCWs were instructed to don a mask or respirator when tending to patients with confirmed or suspected COVID-19, in accordance with the prevailing policy at their institution. HCWs in Canada retained the autonomy to decide whether to wear a mask or N95, irrespective of their assigned intervention.

 Medical Masks as Effective as N95 Respirators. Credit | Getty Images
Medical Masks as Effective as N95 Respirators. Credit | Getty Images

The flaw with this approach, according to Michael Klompas, MD, associate professor of infectious disease at Brigham and Women’s Hospital in Boston and author of seminal studies challenging the conventional wisdom on mask effectiveness against respiratory viruses, is that many HCWs contract the infection from patients with undiagnosed COVID-19.

“What this essentially means is that it is challenging, if not impossible, to attribute participants’ COVID infections in this study to their specific interactions with COVID patients when they were randomized to N95 versus medical masks,” he contended.

Additionally, only 81% of N95 users reported consistent utilization. MacIntyre revealed that she and her colleagues previously published a study demonstrating that N95s must be worn continuously during a shift to be efficacious — including when caring for patients presumed to be non-infectious and performing non-patient care tasks — aligning with the omnipresent risk of airborne transmission in healthcare settings, reports claimed.

“This corresponds with the findings of the Radanovich trial, which demonstrated that targeted utilization of respiratory protection or masks is ineffective,” she remarked, referring to a 2019 study on influenza. “The longer an HCW spends in the hospital (a shift typically lasts 6 to 8 hours), the higher the risk of inhaling accumulated aerosols.” The implication, as posited by CIDRAP research consultant and respiratory protection expert Lisa Brosseau, ScD, CIH, is that such studies may reinforce misperceptions within the healthcare system that masks provide sufficient protection. “It’s a recurrent pattern,” she lamented regarding poorly designed studies.