The use of masks in both community settings and health care settings may slightly reduce the risk of contracting COVID-19, but the evidence base leaves much to be desired, the final setting is alive, a quick review of the few studies found.

“The reliability of the evidence for a reduced risk of SARS-CoV-2 infection with surgical masks compared with no masks remained low based on two previous randomized controlled trials (adjusted prevalence rate 0.89, 95% CI 0.78–0.997 and OR 0. 82, 95% CI 0.52-1.23) and two observational studies, and this is not enough for N95 respirators versus no mask, or cloth mask versus no mask,” wrote Roger Chow, MD, and Tracey Dana , MLS, both from the Oregon Health and Science University in Portland, in Annals of Internal Medicine.

“There were no new studies and insufficient evidence to support surgical and cloth masks and N95 versus surgical masks,” they added.

“While the focus is on higher quality research, the evidence base still has important limitations,” Chow and Dana said. “Randomized controlled trials (RCTs) were few and had some inaccuracies and methodological flaws. In addition, RCTs have evaluated interventions to encourage or encourage mask use and have been designed pragmatically, improving applicability but potentially dampening the intended effects due to suboptimal compliance and overlap.”

Ninth in the series

This article was the ninth in a series of reviews; the first eight looked at a total of two RCTs and 10 observational studies, Chou and Dana explained. “While preparing Update 8, we were aware of the completed RCT of N95 versus surgical masks and were planning for a final update once it was published. The goal of this update is to include this RCT and other new research.”

A total of three RCTs and 21 observational studies were included.

The authors sought answers to two questions: What is the effectiveness and comparative effectiveness of respirators (N95 or equivalent), face masks (surgical), and cloth masks in addition to standard community and healthcare precautions (high versus low risk) settings to prevent SARS-CoV infection -2? And what is the evidence for prolonged or repeated use of N95 respirators to prevent SARS-CoV-2 infection?

To get an answer, they searched PubMed, MEDLINE, and Elsevier EMBASE for relevant studies; they also searched medRxiv and reviewed lists of links to relevant articles. The search for the latest update was conducted from June 2022 to January 2023.

Although they found no new studies on mask use versus no use, one good quality Danish RCT (n = 6024) found that recommending mask use was associated with a small but not statistically significant reduction in COVID risk based on antibody testing. , polymerase chain reaction (PCR) testing, or hospital diagnosis at 1 month (1.8% vs 2.1%; OR 0.82, 95% CI 0.54–1.23).

Chow and Dana reported that there were no differences in mask effects based on age (≤48 vs >48 years), gender, or daily time away from home (≤4.5 vs >4.5 hours). “Furthermore, mask compliance was suboptimal (46% as recommended, 47% predominantly as recommended) and widespread use of other infection control measures may have offset the benefits.”

Benefits of disguise

In studies related to community settings, “observational studies of masks versus no masks consistently found masks to be associated with a reduced risk of SARS-CoV-2 infection, but had methodological limitations and some inaccuracy,” the authors write. “Evidence regarding surgical and cloth masks or more masks versus less consistent mask use is still insufficient.”

In healthcare settings, “a new RCT showed that the effect of instructions for the use of surgical masks is not inferior to instructions for the use of N95 respirators for routine patient care,” they added. “However, non-inferiority was defined as less than a doubling of risk, with a CI corresponding to a risk increase of up to 70%. Due to the imprecision of a single study, the strength of the evidence was low. In addition, RCTs may have reported diminished benefits of N95 respirators in healthcare settings due to infections acquired in the community or at home.”

The researchers listed several limitations in their review. In addition to not attempting a meta-analysis, “we did not formally assess publication bias due to heterogeneity and small numbers of studies for most comparisons,” Chow and Dana wrote. “We limited inclusion to articles in English and excluded environmental and mask policy studies that did not provide information on individual mask use that could provide additional information.”

“Additional studies will refine the comparative effectiveness of masks in preventing SARS-CoV-2 infection,” they added. “Future studies should have sufficient statistical power for primary as well as stratified analysis. Evaluation of masks as a source control is a challenge requiring evaluation of SARS-CoV-2 infections in masked and unmasked communities. Studies should use appropriate methods for diagnosing SARS. -CoV-2, describe the main characteristics of the mask, assess adherence, and evaluate the harm as well as the benefit.”

in on accompanying editorial, annals Editor-in-Chief Christine Lane, MD, and Associate Editor Stephanie Chang, MD, said many questions about masks remain unanswered.

“There is evidence that masks can work to prevent COVID-19, but significant gaps remain as to whether they work and under what conditions,” they wrote. “In the face of future viral outbreaks, we must act quickly to fill the gaps with timely research that avoids the limitations of research done to date. We may never reach the final truth about when the benefits of masking interventions outweigh the harms, but it is imperative that we design studies that fill in information gaps, interpret evidence accurately, and be honest about what we know and what we don’t know. with confidence in making decisions and establishing policies regarding camouflage.”

Masking in health settings is highly recommended

In the accompanying opinionTara Palmore, MD, from George Washington University in Washington, DC, and David Henderson, MD, from the National Institutes of Health, said it would be unwise to stop wearing masks in medical settings.

“Real experience shows the effectiveness of wearing masks in a clinical setting,” they noted. “Thanks in large part to the universal wearing of masks and the use of other personal protective equipment, medical personnel are at much greater risk of contracting COVID-19 from the community than from professional contacts. Transmission from patient to staff and from staff to patient when both are wearing masks does occur, but is unusual.”

They added that “presenteeism”—going to work even when sick—is a well-known problem among clinicians. In an unpublished study conducted at the National Institutes of Health that included contact tracing interviews and subsequent testing for COVID among employees who tested positive, “more than 50% subsequently admitted to having some symptoms consistent with COVID-19 at the time of testing,” written by Palmore and Henderson. . “These data highlight the problem of presenteeism and emphasize the appropriateness of masking.”

However, despite these physicians testing positive, “no transmission to patients has been identified at the facility,” requiring the wearing of masks for physicians and patients, they added.

“In our quest to return to the look and feel of normalcy, and as institutions decide which mitigation strategies to discontinue, we strongly advocate not abandoning this important lesson learned for the safety of our patients.” they concluded.