A randomized intervention trial of mask use and hand hygiene to reduce seasonal influenza-like illness and influenza infections among young adults in a university setting

BACKGROUND: Early efforts to decrease transmission of pandemic influenza will likely rely on nonpharmaceutical interventions (NPIs), because of delays in availability of suitable vaccines and limited stock of antiviral medications. We conducted a randomized trial to estimate reductions in influenza-like illness (ILI) and laboratory-confirmed influenza infection associated with use of face masks combined with hand hygiene measures and face masks alone in a university setting. METHODS: During the 2007-08 influenza season, 1,111 students residing in university residence halls were cluster-randomized by residence house (N=37) to either face mask and hand hygiene, face mask only, or control arms. Discrete-time survival analysis using generalized models estimated rate ratios, according to study arm, each week and cumulatively over the 6-week intervention period, for clinically verified ILI and laboratory-confirmed influenza A or B. RESULTS: In the mask and hand hygiene group compared with the control group, adjusting for covariates, we observed significant reductions in ILI incidence during weeks 4 (RR, 52%, [95% CI, 6%-76%]) and 5 (RR, 62%, [CI, 6%-85%]), and a borderline significant reduction during week 6 (RR, 70%, [CI, 2%-91%]). For laboratory-confirmed influenza, both the face mask only and the face mask and hand hygiene groups compared to the control showed a reduction in cumulative incidence, however results did not reach statistical significance; polymerase chain reaction (PCR) confirmed influenza A or B in 11 out of 49 samples (22%) in the face mask and hand hygiene group, 16 out of 58 samples (28%) in the face mask only group, and 18 out of 68 samples (26%) in the control group. CONCLUSION: These findings suggest that in shared living environments, the use of face masks and hand hygiene may reduce influenza-like illnesses.