Table 1:

Characteristics of studies included in the meta-analysis1117

StudySettingParticipantsOutcomesInterventionsNotes
Randomized controlled trials
Loeb et al., 2009118 hospitals in Ontario, Canada: emergency departments, acute medical units and pediatric units446 nurses; individual-level randomization
  • Laboratory-confirmed respiratory infection, influenza-like illness, workplace absenteeism

  • 5-wk follow-up

  • Intervention: targeted use, fit-tested N95 respirator

  • Control: targeted use, surgical mask

  • Noninferiority trial

  • Detection of influenza A and B, respiratory syncytial virus metapneumovirus, parainfluenza virus, rhinovirus–enterovirus, coronavirus and adenovirus

MacIntyre et al., 2011/201412,1315 hospitals in Beijing: emergency departments and respiratory wards1441 nurses, doctors and ward clerks; cluster randomization by hospital
  • Laboratory-confirmed respiratory infection, influenza-like illness

  • 5-wk follow-up

  • Intervention 1: continual use, fit-tested N95 respirator

  • Intervention 2: continual use, non–fit-tested N95 respirator

  • Control: continual use, surgical mask

Detection of influenza A and B, respiratory syncytial virus metapneumovirus, parainfluenza virus, rhinovirus–enterovirus, coronavirus, adenovirus, Streptococcus pneumoniae, Bordetella pertussis, Chlamydophila pneumoniae, Mycoplasma pneumoniae and Haemophilus influenzae type B
MacIntyre et al., 20131419 hospitals in Beijing: emergency departments and respiratory wards1669 nurses, doctors and ward clerks; cluster randomization by ward
  • Laboratory-confirmed respiratory infection, influenza-like illness

  • 5-wk follow-up

  • Intervention 1: continual use, fit-tested N95 respirator

  • Intervention 2: targeted use, fit-tested N95 respirator

  • Control: continual use, surgical mask

Detection of influenza A and B, respiratory syncytial virus metapneumovirus, parainfluenza virus, rhinovirus–enterovirus, coronavirus, adenovirus, S. pneumoniae, B. pertussis, C. pneumoniae, M. pneumoniae and H. influenzae type B
Cohort study
Loeb et al., 2004152 hospitals in Ontario: coronary care units and ICUs with SARS patients43 nursesLaboratory-confirmed respiratory infection
  • Intervention: N95 respirator

  • Control: surgical mask

  • Retrospective

  • Only 20 nurses reported exposures and consistent use of facial protective equipment

  • Detection of SARS

Case–control studies
Seto et al., 2003165 hospitals in Hong Kong: emergency departments and medicine units13 infected (cases) and 241 noninfected (controls) nurses, doctors, health care assistants and domestic staffLaboratory-confirmed respiratory infection
  • N95 respirator

  • Surgical mask

  • Paper mask

  • No cases in N95 respirator or surgical mask groups

  • 143 controls wore either surgical mask or N95 respirator

  • Detection of SARS

Zhang et al., 20131725 hospitals in Beijing: emergency departments, respiratory wards, ICUs, outpatient departments, technical clinic departments and management51 infected (cases) and 204 noninfected (controls) doctors, nurses, technicians and otherLaboratory-confirmed respiratory infection
  • N95 respirator

  • Surgical mask

  • Cloth mask

  • Cases and controls matched 1:4 by hospital, ward, age and sex

  • 40 cases wore either N95 respirator or surgical mask

  • 159 controls wore either surgical mask or N95 respirator

  • Detection of pandemic H1N1 influenza virus

  • Note: ICU = intensive care unit, SARS = severe acute respiratory syndrome.