Risk factors and effectiveness of preventive measures against influenza in the community

Please cite this paper as: Castilla etal. (2013) Risk factors and effectiveness of preventive measures against influenza in the community. Influenza and Other Respiratory Viruses 7(2) 177183. Background The role of different risk exposures and preventive measures against influenza has not been well established. Objective The aim of this study was to evaluate risk factors and measures to prevent influenza infection in the community. Methods We conducted a multicenter casecontrol study. Cases were 481 outpatients aged 18years or older with laboratory-confirmed influenza A(H1N1)09 in the 20092010 season in Spain. A control was selected for each case from outpatients from the same area matched by age and date of consultation. Information on risk situations, preventive measures and other variables was obtained by interview and review of the medical record. Results In the multivariate conditional logistic regression analysis, the risk of a diagnosis of influenza increased with the number of cohabitants (compared with <3 cohabitants, three cohabitants had an OR=1 center dot 80, 95% CI 1 center dot 122 center dot 89, and 5 cohabitants had an OR=2 center dot 66, 95% CI 1 center dot 315 center dot 41) and for health care workers (OR=2 center dot 94, 95% CI 1 center dot 535 center dot 66). The use of metropolitan public transport was associated with a lower frequency of a diagnosis of influenza (OR=0 center dot 45, 95% CI 0 center dot 300 center dot 68) but not the use of taxis or long-distance transport. The influenza A(H1N1)09 vaccine had a protective effect (OR=0 center dot 13, 95% CI 0 center dot 040 center dot 48), unlike hand washing after touching contaminated surfaces or the use of alcohol-based hand sanitizers. Conclusion The home environment appears to play an important role in the spread of influenza in adults, but not the use of public transport. Health care workers have a higher risk of contracting influenza. Vaccination was the most effective preventive measure.