Abstract
BackgroundFacemasks and respirators have been stockpiled during pandemic preparedness. However, data on their effectiveness for limiting transmission are scarce. We evaluated the effectiveness of facemask use by index cases for limiting influenza transmission by large droplets produced during coughing in households.Methodology and Principal FindingsA cluster randomized intervention trial was conducted in France during the 2008–2009 influenza season. Households were recruited during a medical visit of a household member with a positive rapid influenza A test and symptoms lasting less than 48 hours. Households were randomized either to the mask or control group for 7 days. In the intervention arm, the index case had to wear a surgical mask from the medical visit and for a period of 5 days. The trial was initially intended to include 372 households but was prematurely interrupted after the inclusion of 105 households (306 contacts) following the advice of an independent steering committee. We used generalized estimating equations to test the association between the intervention and the proportion of household contacts who developed an influenza-like illness during the 7 days following the inclusion. Influenza-like illness was reported in 24/148 (16.2%) of the contacts in the intervention arm and in 25/158 (15.8%) of the contacts in the control arm and the difference between arms was 0.40% (95%CI: −10% to 11%, P = 1.00). We observed a good adherence to the intervention. In various sensitivity analyses, we did not identify any trend in the results suggesting effectiveness of facemasks.ConclusionThis study should be interpreted with caution since the lack of statistical power prevents us to draw formal conclusion regarding effectiveness of facemasks in the context of a seasonal epidemic.Trial Registrationclinicaltrials.gov NCT00774774
Highlights
Influenza virus is responsible for annual epidemics worldwide and causes a significant public health burden
The threat of a severe H5N1 pandemic caused by avian influenza and the recent worldwide spreading of influenza H1N1v have renewed interests in nonpharmaceutical interventions for limiting influenza transmission
We evaluated the effectiveness of surgical facemasks for limiting influenza transmission by large droplets produced during coughing
Summary
Influenza virus is responsible for annual epidemics worldwide and causes a significant public health burden. Facemasks and respirators have been stockpiled during pandemic preparedness and are currently recommended in several countries Data on their effectiveness for limiting transmission are scarce. Five randomized trials evaluating facemasks and hand hygiene with different designs and objectives have been recently published [2,3,4,5,6]. Three of these trials were conducted in families and did not show significant improvements in their primary analyses in intervention groups versus the control groups [2,3,4]. We evaluated the effectiveness of facemask use by index cases for limiting influenza transmission by large droplets produced during coughing in households
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