Joseph's Healthcare, Hamilton, Ontario, Canada (M.C.); Niagara Health System, Niagara, Ontario, Canada (K.A.).
Brantford Community Health System, Brantford, Ontario, Canada (V.G.).Department of Medicine, McMaster University and Hamilton Health Sciences, Hamilton, Ontario, Canada (D.M., R.H.).Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada (J.A.L.).Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada (S.B.).It is uncertain if medical masks offer similar protection against COVID-19 compared with N95 respirators.This randomized trial, which enrolled participants in Canada, Israel, Pakistan, and Egypt, aimed to determine whether medical masks are noninferior to N95 respirators to prevent COVID-19 in health care workers providing routine care.
It is uncertain if medical masks offer similar protection against COVID-19 compared with N95 respirators.To determine whether medical masks are noninferior to N95 respirators to prevent COVID-19 in health care workers providing routine care.29 health care facilities in Canada, Israel, Pakistan, and Egypt from 4 May 2020 to 29 March 2022.1009 health care workers who provided direct care to patients with suspected or confirmed COVID-19.In the intention-to-treat analysis, RT-PCR–confirmed COVID-19 occurred in 52 of 497 (10.46%) participants in the medical mask group versus 47 of 507 (9.27%) in the N95 respirator group (hazard ratio [HR], 1.14 [95% CI, 0.77 to 1.69]).An unplanned subgroup analysis by country found that in the medical mask group versus the N95 respirator group RT-PCR–confirmed COVID-19 occurred in 8 of 131 (6.11%) versus 3 of 135 (2.22%) in Canada (HR, 2.83 [CI, 0.75 to 10.72]), 6 of 17 (35.29%) versus 4 of 17 (23.53%) in Israel (HR, 1.54 [CI, 0.43 to 5.49]), 3 of 92 (3.26%) versus 2 of 94 (2.13%) in Pakistan (HR, 1.50 [CI, 0.25 to 8.98]), and 35 of 257 (13.62%) versus 38 of 261 (14.56%) in Egypt (HR, 0.95 [CI, 0.60 to 1.50]).
There were 47 (10.8%) adverse events related to the intervention reported in the medical mask group and 59 (13.6%) in the N95 respirator group.
Among health care workers who provided routine care to patients with COVID-19, the overall estimates rule out a doubling in hazard of RT-PCR–confirmed COVID-19 for medical masks when compared with HRs of RT-PCR–confirmed COVID-19 for N95 respirators.Health care workers use either medical masks, also called surgical masks, or N95 respirators for the routine care of patients with COVID-19 as a component of their personal protective equipment.Medical masks are recommended by the World Health Organization for routine care (1, 2), whereas N95 respirators are recommended by the Centers for Disease Control and Prevention for the routine care of patients with COVID-19 (3–5).
It is uncertain if medical masks offer similar protection against COVID-19 compared with N95 respirators (6).We conducted an international pragmatic randomized controlled trial where health care workers were randomly assigned to either medical masks or N95 respirators when providing routine care to patients with suspected or confirmed COVID-19.This pragmatic, randomized, open-label, multicenter trial initially aimed to assess whether medical masks were noninferior to N95 respirators for protection against COVID-19 among unvaccinated nurses providing routine care to patients with suspected or confirmed COVID-19 (see the study protocol and statistical analysis plan).Before trial commencement, in addition to nurses, other health care workers were made eligible to increase enrollment, and follow-up was reduced from 12 to 10 weeks to minimize loss to follow-up.
As circulation of SARS-CoV-2 increased, health care workers known to have a previous laboratory-confirmed clinical diagnosis of COVID-19 at the time of enrollment were excluded.
The trial enrolled participants in 29 health care facilities: 17 acute care hospitals in Canada, 4 acute care hospitals in Pakistan, 2 long-term care facilities in Israel (facilities where trained medical staff are always available to assist residents and where high-flow oxygen and medication via inhalation could be administered), and 6 acute care hospitals in Egypt.The trial was restricted to health care settings where the policy was to use medical masks while providing routine care to patients with confirmed or suspected COVID-19.
Health care workers who provided direct care to patients with suspected or confirmed COVID-19 in specialized COVID-19 units and in emergency departments, medical units, pediatric units, and long-term care facilities were enrolled; intensive care units were not included in the study.Health care workers were required to spend 60% or more of their time doing clinical work when enrolled.
Health care workers were excluded if they did not have a valid fit test within the past 24 months or could not pass a fit test, had 1 or more high-risk comorbidities for COVID-19 (hypertension, cardiac disease, pulmonary disease, chronic kidney disease, diabetes, chronic liver disease, actively treated cancer, or immunosuppression due to illness or medications), had a previous laboratory-confirmed clinical diagnosis of COVID-19 at the time of enrollment, or had received 1 or more doses of a COVID-19 vaccine with greater than 50% efficacy for the circulating strain (for example, mRNA or vector-based COVID-19 vaccine against the original SARS-CoV-2 strain).Investigators were blinded to the group assignment, but it was not possible to conceal the identity of the medical mask or N95 respirator assignment to the study staff or participants.
Health care workers randomly assigned to the medical mask group were instructed to use the medical mask when providing routine care to patients with COVID-19 or suspected COVID-19, which aligned with the current policy in their setting.The ASTM International certified masks were provided to the health care workers either by their health care facility or by the study (Supplement Table 1).
As part of the trial protocol, health care workers could also use the N95 respirator at any time based on a point-of-care risk assessment.
Health care workers randomly assigned to the N95 respirator group were instructed to use a fit-tested National Institute for Occupational Safety and Health–approved N95 respirator when providing routine care to patients with COVID-19 or suspected COVID-19.Participants were required to use the type of device they were allocated to, either a medical mask or an N95 respirator, for 10 weeks.
This refers to the use of a mask when in the health care facility for all activities, whether patient related or not, including in workrooms, meetings, and treating persons that were not suspected or known to be positive for COVID-19.
Participants were asked to report the extent to which they used the mask that they were assigned to on a weekly basis—that is, “During your last work shift, to what extent did you wear the mask you were assigned,” where the possible responses were “Always,” “Sometimes,” “Never,” or “Do not recall.” In both study groups, health care workers were required to use the N95 respirator for aerosol-generating medical procedures, as this was in keeping with their institutional policies.
Participants were asked to discard the medical mask or N95 respirator if it became soiled or damaged or if breathing through the device became difficult.
Adherence to the assigned medical mask or N95 respirator for routine care and to hand hygiene was measured using weekly self-reporting for all participants and external monitoring wherever feasible.To conduct the audits of adherence to the intervention (medical mask or N95 respirator), the coordinating center randomly selected 20% of shifts at a health care facility, and during these shifts, trial participants were observed.
Reported exposures and potential exposures to COVID-19, including community and home exposure, hospital exposures, participation in aerosol-generating procedures, and hospital outbreaks (as defined by the health care facility) were measured.
Outcomes were analyzed on an intention-to-treat basis, defined by medical mask or N95 respirator assignment and follow-up until 10 weeks or 2 weeks after the first mRNA vaccine dose.Between 4 May 2020 and 12 January 2022, a total of 1191 health care workers were assessed for eligibility, and 1009 were enrolled.There were 500 randomly assigned to medical masks and 509 to the N95 respirator (Figure 1).
Overall, there were 185 (37.5%) participants in the medical group versus 185 (37.2%) in the N95 respirator group who were seronegative at baseline—that is, had no SARS-CoV-2 spike IgG or nucleocapsid IgG antibodies at baseline.
The mean duration of follow-up was similar between the 2 study groups—9.06 weeks in the medical mask group and 9.03 weeks in the N95 respirator group.
Five participants who were randomly assigned but never followed were excluded from analysis—3 in the medical mask group (1 was previously positive for COVID-19 on RT-PCR and 2 withdrew) and 2 in the N95 respirator group (1 was previously positive for COVID-19 on RT-PCR and 1 withdrew) (Figure 1).
Of the resulting 1004, follow-up was complete (that is, full 10 weeks or 14 days after first vaccination) in 483 (97.1%) in the medical mask group and 489 (96.4%) in the N95 respirator group.
The primary outcome in the intention-to-treat analysis, RT-PCR–confirmed COVID-19, occurred in 52 of 497 (10.46%) in the medial mask group versus 47 of 507 (9.27%) in the N95 respirator group (HR, 1.14 [95% CI, 0.77 to 1.69]).In an unplanned subgroup analysis by country, we found that in the medical mask group versus N95 respirator group, RT-PCR–confirmed COVID-19 occurred in 8 of 131 (6.11%) versus 3 of 135 (2.22%) in Canada (HR, 2.83 [CI, 0.75 to 10.72]), 6 of 17 (35.29%) versus 4 of 17 (23.53%) in Israel (HR, 1.54 [CI, 0.43 to 5.49]), 3 of 92 (3.26%) versus 2 of 94 (2.13%) in Pakistan (HR, 1.50 [CI, 0.25 to 8.98]), and 35 of 257 (13.62%) versus 38 of 261 (14.56%) in Egypt (HR, 0.95 [CI, 0.60 to 1.50]) (Figure 2).
There were 86 of 8338 (1%) weekly surveys missing in the medical mask group and 65 of 8468 (0.8%) missing in the N95 respirator group.There were 2 participants who had serious adverse events in the medical mask group (both hospitalizations for COVID-19, where 1 had confirmed pneumonia) and 1 participant in the N95 respirator group (hospitalization for COVID-19 pneumonia).In addition, there were 3 participants (2 in the medical mask group and 1 in the N95 respirator group) who could not be safely isolated at home and were hospitalized for isolation.
There were 47 (10.8%) adverse events related to the intervention reported in the medical mask group and 59 (13.6%) in the N95 respirator group (Supplement Table 4).
There was 1 participant in the medical mask group and 3 in the N95 respirator group who withdrew because of discomfort or adverse events related to the device they were assigned.
Mean cycle threshold values of patients positive for COVID-19 were less than 30 in 84% of the 25 study units where these data were collected (Supplement Table 10).
Adherence with the assigned medical mask or N95 respirator was self-reported as “always” in 91.2% in the medical mask group versus 80.7% in the N95 respirator group and as “always” or “sometimes” in 97.7% in the medical mask group versus 94.4% in the N95 respirator group (Supplement Table 13).Of 118 participants observed in the medical mask group, 116 (98.3%) were reported by monitors to be adherent to their assigned mask—14 (100%) in Pakistan and 102 (98%) in Egypt.
Among health care workers who took care of patients with suspected or confirmed COVID-19, although the upper limit of the CIs of the pooled estimate for medical masks when compared with N95 respirators for preventing RT-PCR–confirmed COVID-19 was within the noninferiority margin of 2, this margin was wide, and firm conclusions about noninferiority may not be applicable given the between-country heterogeneity.Enrollment in Canada occurred early in the pandemic in acute health care facilities.
The relative protection of medical masks compared with N95 respirators varied by country.
However, this finding does not seem to be explained by differences in baseline seropositivity given that a post hoc analysis of the effect of medical masks versus N95 respirators on RT-PCR–confirmed COVID-19 that was restricted to participants seronegative at baseline led to similar within-country point estimates compared with analyses that included the seropositive participants.
Point estimates of the HRs for medical masks versus N95 respirators for both Israel and Pakistan were similar (HRs of 1.54 and 1.50).For Canada, the point estimate of 2.83 is suggestive of an increased risk with the medical mask, however, the absolute number of events is small.
It is notable that there was a close to null effect of medical masks compared with N95 respirators in Egypt, where Omicron was circulating, and from where over half of our participants were enrolled.It is possible that a higher rate of community transmission could have obscured a higher rate of infection with the medical mask versus the N95 respirator, in contrast to what was seen in Canada.
It is also possible that given the high rate of exposure to patients with COVID-19 reported by health care workers in Egypt with the more transmissible Omicron, the results reflect no difference between the groups in health care acquisition of RT-PCR–confirmed COVID-19.
Although self-reported adherence was lower in the N95 respirator group, the randomly conducted audited adherence was similar in both groups—98.3% in the medical mask group versus 96.6% in the N95 respirator group.We acknowledge concerns of suboptimal filtering capacity of medical masks, but the trial was done strictly in settings where the policy was use of medical masks for routine care, and no participants who were using N95 respirators were asked to use medical masks.
In Pakistan and Egypt, the trial offered superior-quality medical masks and N95 respirators to participants who would otherwise not have access.
Furthermore, participants who believed they were at high risk during a particular exposure were allowed to use the N95 respirator if assigned to a medical mask.
In conclusion, among health care workers who provided routine care to patients with COVID-19, the overall estimates rule out a doubling in hazard of RT-PCR–confirmed COVID-19 for medical masks when compared with HRs of RT-PCR–confirmed COVID-19 for N95 respirators.Department of Pathology and Molecular Medicine and Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada (M.L.).Department of Medicine, McMaster University and Hamilton Health Sciences, Hamilton, Ontario, Canada (D.M., R.H.).Joseph's Healthcare, Hamilton, Ontario, Canada (M.C.); Niagara Health System, Niagara, Ontario, Canada (K.A.).
Michael's, Toronto, Ontario, Canada (M.M.).
Brantford Community Health System, Brantford, Ontario, Canada (V.G.).Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada (J.A.L.).Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada (S.B.).University of Toronto, Toronto, Ontario, Canada (E.P.).Corresponding Author: Mark Loeb, MD, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada; e-mail, [email protected]ca.
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