Systematic reviews and meta-analyses
| First author, year [ref.] | Total studies (n) | Relevant studies/total studies in meta-analysis (n/n) | Population | Interventions | Outcome | Findings |
| Low quality | ||||||
| Chu, 2020 [14] | 172 | 3/44 Observational studies | General community# Household | Facemask | Probable or confirmed SARS-CoV-1 infection | Facemask use by those exposed to infected contacts decreases the risk of infection (relative risk 0.56, 95% CI 0.40–0.79; low–moderate credibility) |
| Jefferson, 2020 [10] | 67 | 16/35 Hand hygiene RCTs | School Childcare centre Household Workplace Military (navy) Assisted-living facility Mass gatherings General community# | Hand hygiene | ARI Laboratory-confirmed influenza Laboratory-confirmed other virus Sick leave | Hand hygiene decreases the composite outcome of ARI, ILI or laboratory-confirmed influenza relative to control (risk ratio 0.89, 95% CI 0.84–0.95; low-certainty evidence) with high heterogeneity Hand hygiene reduces the risk of ARI relative to control (risk ratio 0.84, 95% CI 0.82–0.86; moderate-certainty evidence) Hand hygiene does not reduce the risk of ILI and laboratory-confirmed influenza (risk ratio 0.91, 95% CI 0.63–1.30; low-certainty evidence) Hand hygiene reduces the rate of sick leave compared to control (risk ratio 0.64; 95% CI 0.58–0.71) |
| Facemask | Mask results were not differentiated between community and healthcare settings | |||||
| Facemask and hand hygiene | Hand hygiene with facemasks does not reduce the risk of ILI (risk ratio 1.03, 95% C1 0.77–1.37) or laboratory-confirmed influenza (risk ratio 0.99, 95% CI 0.69–1.36) compared to control | |||||
| Gargling | Gargling does not reduce the risk of viral illness compared to control (risk ratio 0.91, 95% CI 0.63–1.31) | |||||
| Wong, 2014 [15] | 18 | 10/10 RCTs | Household School Workplace | Hand hygiene | ILI Laboratory-confirmed influenza | Hand hygiene alone compared to control does not demonstrate a significant benefit for ILI (risk ratio 0.86, 95% CI 0.71–1.04) and laboratory-confirmed influenza (risk ratio 0.90, 95% CI 0.67–1.20) |
| Hand hygiene and facemask | Hand hygiene with facemask use compared to control is associated with significantly decreased ILI (risk ratio 0.73, 95% CI 0.6–0.89) and laboratory-confirmed influenza (risk ratio 0.73, 95% CI 0.53–0.99) | |||||
| Hand hygiene ± facemask | Hand hygiene with or without facemask compared to control is associated with a significant decrease in ILI (risk ratio 0.78, 95% CI 0.68–0.9), but a nonsignificant effect on laboratory-confirmed influenza (risk ratio 0.82, 95% CI 0.66–1.02) Subgroup analysis of less-developed countries for the same interventions and outcomes does not demonstrate statistically significant results | |||||
| Critically low quality | ||||||
| Abdullahi, 2020 [16] | 17 | 7/7 RCTs and observational studies | Low- to middle-income countries (China, Bangladesh, Thailand) Household School General community# | Facemask | SARS and influenza incidence | Facemask use demonstrates no significant benefit to the composite of influenza and SARS spread versus control (risk ratio 0.78, 95% CI 0.36–1.67) |
| Hand hygiene | Hand hygiene demonstrates no significant benefit to SARS and influenza spread versus control (risk ratio 0.95, 95% CI 0.83–1.08) | |||||
| Facemask and hand hygiene | Facemasks with hand hygiene demonstrates no significant benefit to influenza spread versus control (risk ratio 0.94, 95% CI 0.58–1.54) | |||||
| Social distancing | Social distancing interventions may slow down the spread of influenza (low-certainty evidence, 9 studies not pooled) | |||||
| Aggarwal, 2020 [17] | 9 | 8/9 RCTs | Household School | Facemask | Clinically diagnosed influenza or ILI | Facemasks show no significant reduction of ILI compared to control (effect size −0.17, 95% CI −0.43–0.10)¶ |
| Facemask and hand hygiene | Mask and hand hygiene show no significant reduction of ILI compared to control (effect size −0.09, 95% CI −0.58–0.4)¶ | |||||
| Gera, 2018 [18] | 41 | 8/34 RCTs and non-RCTs | Low- to middle-income countries Individuals, families or communities Children aged <18 years | Hand hygiene | ARI Laboratory-confirmed influenza School sick leave | Hand hygiene compared to control decreases the risk of ARI (risk ratio 0.76, 95% CI 0.59–0.98), 6 studies, moderate-quality evidence Hand hygiene compared to control decreases laboratory-confirmed influenza (risk ratio 0.5, 95% CI 0.41–0.62), 1 study, very low quality evidence Hand hygiene compared to control decreases school sick leave (risk ratio 0.78, 95% CI 0.76–0.8), 4 studies, moderate-quality evidence |
| Liang, 2020 [19] | 21 | 8/8 RCTs and observational studies | School Mass-gathering (Hajj) Workplace Household General community# | Facemask | Laboratory confirmed respiratory virus Clinically diagnosed ARI | Facemask use compared to control significantly reduces laboratory-confirmed viral infection by 47% (OR 0.53, 95% CI 0.36–0.79) |
| Rabie, 2006 [20] | 8 | 8/8 RCTs and interventional studies | School Childcare centre Military (navy) | Hand hygiene | ARI Duration of respiratory illness | Hand hygiene measures lower risk of respiratory infection by 24% (relative risk 0.76, 95% CI 0.6–0.96) Sensitivity analysis excluding one uncontrolled study of hand hygiene measures (n=7) demonstrate decreased risk of respiratory infection by 16% (relative risk 0.84, 95% CI 0.79–0.89); note, studies were of poor quality Sensitivity analysis excluding crossover or poor-quality studies had no significant effect |
| Rainwater-Lovett, 2014 [21] | 37 | 10 personal protective equipment | Assisted-living facility | Personal protective equipment (hand hygiene, mask, droplet precautions) | ILI with minor variations Laboratory-confirmed influenza All studies required laboratory testing to establish influenza as the cause of the outbreak | Personal protective equipment is not associated with decreased influenza A or B attack rate (OR 0.63, 95% CI 0.33–1.19) |
| 18 social distancing | Social distancing (no new admissions, visitor restriction, ward transfer restrictions, isolation or cohorting) | Social distancing is not associated with decreased influenza A or B attack rate (OR 1.31, 95% CI 0.78–2.18) | ||||
| Wang, 2020 [22] | 15 | 10/10 observational studies | School Household Mass gathering (Hajj) In-flight setting | Facemask ± hand hygiene | ARI Laboratory-confirmed influenza | Facemask use is not associated with reduced ARI incidence (OR 0.96, 95% CI 0.8–1.15) Subgroup analysis of laboratory-confirmed viral infection (OR 0.82, 95% CI 0.63–1.07) does not demonstrate any benefit Subgroup analysis of self-reported/clinically diagnosed ARI (OR 1.1, 95% CI 0.84–1.45) does not demonstrate any benefit |
| Xiao, 2020 [23] | 18 | 12/12 hand-hygiene studies 10/10 facemask studies | School Household Mass gathering | Facemask and hand hygiene | Laboratory-confirmed influenza | Facemask use with hand hygiene does not significantly decrease laboratory-confirmed influenza (risk ratio 0.91, 95% CI 0.73–1.13; 6 studies) |
| Facemask | Facemask use alone does not significantly decrease laboratory-confirmed influenza (risk ratio 0.78, 95% CI 0.51–1.20; 7 studies) | |||||
| Facemask ± hand hygiene | Facemask use with or without hand hygiene does not decrease laboratory-confirmed influenza (risk ratio 0.92, 95% CI 0.75–1.12; 10 studies) | |||||
| Hand hygiene | No pooled estimate for hand hygiene alone or with optional facemask use due to high heterogeneity |
SARS-CoV: severe acute respiratory syndrome coronavirus; ARI: acute respiratory illness; ILI: influenza-like illness; RCT: randomised controlled trial. #: general community settings refer to all other community-based settings not fitting into any of the major categories such as school, household, assisted living facility, childcare centre or workplace. ¶: the effect size was calculated as log(OR). A negative number represents a protective effect.