Non-pharmaceutical interventions to reduce influenza transmission in households: a systematic review and meta-analysis

•Non-pharmaceutical interventions (NPI) play an important role in influenza control.•Most countries recommended face masks and hand hygiene as NPIs in households.•We identified nine randomized controlled trials for face masks and hand hygiene.•Hand hygiene and face masks did not affect household transmission.•Within-household NPIs would be effective when implemented soon after symptom onset. Background: Influenza pandemic plans often recommend non-pharmaceutical interventions (NPIs) in household settings, including hand hygiene and face masks. We reviewed the evidence supporting the recommendations of these measures to prevent the spread of influenza in households. Methods: We performed systematic reviews between 26 May and 30 August 2022 in Medline, PubMed, EMBASE, and CENTRAL to identify evidence for the effectiveness of selected measures recommended by representative national influenza pandemic plans. We prioritized evidence from randomized controlled trials conducted during influenza pandemics and seasonal influenza epidemics. Fixed-effects models were used to estimate the overall effects. Systematic reviews were registered in the OSF registry (https://osf.io/8kyth). Results: We selected 9 NPIs for evidence review. We identified 9 randomized-controlled trials related to hand hygiene and face masks in household settings. 2 studies reported that measures could delay the introduction of influenza virus infections into households. However, we did not identify evidence from randomized controlled trials that indicated a substantial effect of hand hygiene and face masks in preventing the spread of influenza within households. Conclusion: Limited evidence indicated that within-household measures may likely be effective only when implemented before or as soon as possible after symptom onset in an infected case. Improving the evidence base for NPIs in households and elsewhere is a continuing priority. Funding: World Health Organization and the Strategic Topic Grants Scheme