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Table 2 Non-intervention studies’ characteristics

From: The effectiveness of hand hygiene interventions for preventing community transmission or acquisition of novel coronavirus or influenza infections: a systematic review

Study ID Country Aim of the study Study design Population Sample size Type of infection Method of identifying infection Relevant outcomes Findings
Abd [33] Iraq To identify the risk factors predisposing to SARS-CoV-2 infection Retrospective cross-sectional survey General public N = 348 hospitalised COVID-19 cases & 348 hospitalised non-COVID-19 patients SARS-CoV-2 Confirmed in the hospital (no details provided) Risk factors for SARS-CoV-2 acquisition Amongst confirmed COVID-19 cases, 66 (18.96%) reported washing their hands “healthily”, whereas 148 (42.52%) reported doing so sometimes, compared to 94 (27.01%) and 134 (38.50%) non-COVID-19 patients, respectively.
There was a statistically significant association between COVID-19 infection and hand washing (p < 0.001).
Badri et al. [34] USA To identify behaviours and evaluate trends in COVID-19-mitigating practices in a predominantly Black and Hispanic population, to identify differences in practices by self-reported ethnicity, and to evaluate whether federal emergency financial assistance was associated with SARS-CoV-2 acquisition Retrospective cross-sectional survey General public N = 209 individuals who tested positive for SARS-CoV-2 & 105 who tested negative SARS-CoV-2 Laboratory confirmed Risk factors for SARS-CoV-2 acquisition Frequent use of ABHR was associated with lower odds of infection (aOR: 0.26; 95% CI: 0.13, 0.52), but frequent hand washing showed no significant effect (aOR: 0.55; 95% CI: 0.21, 1.44).
Castilla et al. [26] Spain To evaluate risk factors and measures to prevent influenza infection in the community Retrospective case-control study General public N = 481 influenza outpatients & 481 controls Influenza Laboratory confirmed Risk factors for influenza acquisition The frequency of hand washing 5–10 times (aOR: 0.87; 95% CI: 0.54, 1.39; p = 0.56), and > 10 times (aOR: 0.98; 95% CI: 0.59, 1.64; p = 0.94), the use of ABHR (aOR: 1.36; 95% CI: 0.85, 2.19; p = 0.2) and hand washing after touching contaminated surfaces (aOR: 0.70; 95% CI: 0.44, 1.11; p = 0.13) had no significant protective effect.
Doshi et al. [28] Bangladesh To identify household-level factors associated with influenza among young children in a crowded community in Dhaka Prospective case-control study Pre-school children N = 145 households of influenza paediatric cases & 341 control households Influenza Laboratory confirmed Risk factors for influenza acquisition The mean hand washing frequency during a 5-hour observation period was similar between case (0.64 events) and control (0.63 events) households (p = 0.87). Mean daily soap consumption per capita was 2.92 and 2.93 in the case and control households, respectively (p = 0.92).
Almost all case (97%) and control (99%) households had water present at the primary hand washing location, but 22% of case households and 29% of control households had soap present before it was provided for soap consumption measurement (p = 0.08).
Doung-ngern et al. [35] Thailand To evaluate the effectiveness of personal protective measures against SARS-CoV-2 infection in public Retrospective case-control study General public N = 211 cases & 839 controls SARS-CoV-2 Laboratory confirmed Risk factors for SARS-CoV-2 transmission (secondary attack rates) A significant, negative association was found between risk for SARS-CoV-2 infection and washing hands “often” (aOR: 0.33; 95% CI: 0.13, 0.87) or “sometimes” (aOR: 0.34; 95% CI: 0.14, 0.81); p = 0.045.
Godoy et al. [27] Spain To investigate the effectiveness of non-pharmacological interventions in preventing cases of influenza requiring hospitalization Retrospective case-control study General public N = 813 hospitalized influenza cases & N = 2274 controls Influenza Laboratory confirmed Protective factors against influenza acquisition The frequency of hand washing 5–10 times (aOR: 0.65; 95% CI: 0.52, 0.84; p = 0.001) and > 10 times (aOR: 0.59; 95% CI: 0.44, 0.79, p < 0.001) and hand washing after contact with contaminated surfaces (aOR: 0.65; 95% CI: 0.50, 0.84; p = 0.001) were protective factors and were dose-responsive (p < 0.001). ABHR showed no significant protective effect (aOR: 0.82; 95% CI: 0.65, 1.02; p = 0.08).
Karout et al. [36] USA To determine the prevalence, level of COVID-19 risk perception attitude and preventive behaviour implemented by the Latino population in the USA Prospective cross-sectional survey General public N = 410 asymptomatic Latino adults SARS-CoV-2 Laboratory-confirmed Preventive factors associated with SARS-CoV-2 acquisition Participants who tested positive (n = 76; 18.5%) were significantly less likely to use ABHR and wash hands compared with participants who tested negative (p < 0.001).
Lau et al. [30] China To delineate the distribution of different sources of SARS transmission, identify the undefined source group and to identify relevant risk and protective factors associated with contracting SARS Retrospective case-control study General public N = 330 suspected SARS cases with undefined infection sources & 660 controls SARS-CoV-1 SARS case definition criteria Risk and preventive factors associated with SARS-CoV-1 acquisition Frequent hand washing (more than 10 times a day) was a significant protective factor (OR: 0.58; 95% CI: 0.38, 0.87; p = 0.008).
Lio et al. [37] China To determine the risk and protective factors for COVID-19 infection at the individual level, with a specific emphasis on personal behaviours such as mask use, the number of gatherings, and HH practices Retrospective case-control study General public N = 24 hospitalised COVID-19 patients & 1113 control participants who completed quarantine after travelling from COVID-19 high-risk foreign country SARS-CoV-2 Laboratory-confirmed Risk and preventive factors associated with SARS-CoV-2 acquisition Compared to the non-infected individuals, those with SARS-CoV-2 infection were significantly less likely to wash hands after contact with individuals who had respiratory symptoms (50% vs. 95.3%; p = 0.005), but not after contact with suspected or confirmed COVID-19 patients (50% vs. 95.2%; p = 0.057).
Hand washing after outdoor activity (aOR: 0.021; 95% CI: 0.003, 0.134;  p < 0.005), hand washing before touching the mouth and nose area (aOR: 0.303; 95% CI: 0.114, 0.808; p < 0.05) were found to be independent factors for COVID-19 infection.
Amongst infected individuals, 16.7% reported always washing hands for over 20 seconds each time, compared with 31.9% in the non-infected group (p = 0.125).
Liu et al. [38] USA To understand the risk of SARS-CoV-2 transmission from a paediatric primary index case to household contacts living in Los Angeles County Prospective cohort study Children N = 15 paediatric index cases & 50 household contacts SARS-Cov-2 Laboratory-confirmed Risk factors for SARS-CoV-2 transmission (secondary attack rates) Overall secondary attack rates were 34% (95% CI: 22, 48%).
Transmission was significantly lower in households with increased hand washing or ABHR use compared with those who did not report increased hand washing or ABHR use (19%; 95% CI: 9, 36) vs. 58%; 95% CI: 36, 77; p = 0.01).
Speaker et al. [39] USA To compare the social behaviours of individuals who were tested positive for COVID-19 relative to non-infected individuals Retrospective case-control study General public N = 113 COVID-19 cases & 226 controls SARS-Cov-2 Laboratory confirmed Risk factors for SARS-CoV-2 acquisition 67% of cases and 63% of controls reported always washing hands or using ABHR after possible exposures (p = 0.24). 75% of cases and 74% of controls reported always washing hands for at least 20 seconds (p = 0.60).
Wilson-Clark et al. [31] Canada To determine characteristics associated with the transmission of SARS within households Retrospective cross-sectional survey General public N = 74 SARS-affected households SARS-Cov-1 SARS case definition criteria Risk factors for household transmission of SARS-CoV-1 Failure to wash hands after caring for ill person (RR: 3.46; 95% CI: 1.10, 10.92) and not always washing hands after changing a diaper (RR: 3.94; 95% CI: 1.28, 12.10) were associated with an increased risk of transmission.
Torner et al. [25] Spain To investigate the effectiveness of non-pharmaceutical interventions in preventing cases of influenza in children in the community setting in 2009 pandemic and 2010–2011 post pandemic/seasonal epidemic Retrospective case-control study Children N = 239 confirmed paediatric influenza outpatients & 239 controls Influenza Laboratory-confirmed Risk factors for influenza acquisition Hand washing more than 5 times per day (aOR: 0.62; 95% CI: 0.39, 0.99; p = 0.04) was the only statistically significant protective factor.
For 5–17 age group, there was a negative association for influenza infection for both washing more than 5 times per day (aOR: 0.47; 95% CI: 0.22, 0.99; p = 0.04) and hand washing after touching contaminated surfaces (aOR: 0.19; 95% CI: 0.04, 0.86; p = 0.03).
For the 0–4 years group there was no significant association for washing hands more than 5 times per day (aOR: 0.91; 95% CI: 0.46, 1.78; p = 0.77) nor for hand washing after touching contaminated surfaces (aOR: 1.06; 95% CI: 0.44, 2.56; p = 0.77).
Wu et al. [32] China To compare exposures of unlinked, probable SARS patients with community-based matched controls Retrospective case-control study General public N = 94 probable SARS patients & N = 281 controls SARS-Cov-1 Laboratory confirmed Risk and preventive factors associated with SARS-CoV-1 acquisition Always washing hands when returning home was a protective factor (OR: 0.3; 95% CI: 0.2, 0.7; p = 0.003).
No significant association was found for always washing hands before eating (OR: 0.6; 95% CI: 0.3, 1.1; p = 0.11) or after using restrooms (OR: 0.5; 95% CI: 0.2, 1.2; p = 0.10).
Xie et al. [40] China To quantify exposure patterns, transmission characteristics, and the clinical spectrum of SARS-CoV-2 infection Retrospective cohort study General public N = 20 index patients hospitalized with severe COVID-19 & 79 of their household contacts SARS-Cov-2 Laboratory confirmed Risk factors for SARS-CoV-2 transmission Hand washing ≥5 times/day was associated with reduced infection risk (52.8% vs.76.9%, p = 0.04).
Zhang et al. [29] China To assess risk factors associated with household transmission of pandemic H1N1 from self-quarantined patients in Beijing Retrospective case-control study General public N = 54 case households & 108 control households Influenza Laboratory confirmed Risk factors for influenza transmission Hand washing ≥3/day was related to the household transmission of pandemic H1N1 from self-quarantined patients (OR: 0.71; 95% CI: 0.48, 0.94; p = 0.05).
  1. ABHR alcohol-based hand rub, aOR adjusted odds ratio, CI confidence intervals, H1N1 Hemagglutinin Type 1 and Neuraminidase Type 1 (swine flu strain), p p-value, RR relative risk, SARS-CoV-1 severe acute respiratory syndrome coronavirus 1, SARS-CoV-2 severe acute respiratory syndrome coronavirus 2