A systematic literature review was undertaken to identify and evaluate the published literature on NPI efficacy to prevent human transmission of influenza virus in adults. Reviewers assessed the quality of eligible studies utilising the Critical Appraisal Skills Programme for bias and the Scottish Intercollegiate Guidelines Network for methodological quality. Studies were assessed for risk of bias domains of random sequence generation, allocation concealment, attribution bias, selective reporting and blinding.
2247 relevant citations were reduced to 100 for full text evaluation. Only seven met all selection criteria and pooled analysis was not feasible. Of the seven studies, two were randomised controlled trials (RCTs) and five were cluster RCTs. The main NPIs studied were disinfection and hygiene; barriers; and combined NPIs. However these seven RCTs had significant design flaws. Only two studies used laboratory confirmed influenza and poor statistical power was a major problem. Positive significant interventions included professional oral hygiene intervention in the elderly and hand-washing.
Despite the potential for NPI in preventing influenza transmission there is very limited data available. Hand washing and dental hygiene may be useful but other interventions have not been fully assessed. Properly designed studies evaluating large populations including 'at risk' patients and in a variety of communities are needed.