Findings of a cluster randomized controlled trial of face masks and hand hygiene to prevent influenza transmission in households
Session I – Cowling, Benjamin – Abstract 2 of 3
Title of Contribution: Findings of a cluster randomized controlled trial of face masks and hand hygiene to prevent influenza transmission in households
Author(s): Benjamin J. Cowling1, Kwok-Hung Chan2, Vicky J. Fang1, Calvin K. Y. Cheng1, Rita O. P. Fung1, Winnie Wai1, Joey Sin1, Wing Hong Seto3, Raymond Yung4,5, Daniel W. S. Chu3, Billy C. F. Chiu5, Paco W. Y. Lee6, Ming Chi Chiu7, Hoi Che Lee8, Timothy M. Uyeki9, Peter M. Houck10, J. S. Malik Peiris2, Gabriel M. Leung1
Affiliation(s): (1) School of Public Health, the University of Hong Kong, Hong Kong; (2) Department of Microbiology, the University of Hong Kong, Hong Kong; (3) Hospital Authority, Government of the Hong Kong SAR, Hong Kong; (4) Centre for Health Protection, Department of Health, Government of the Hong Kong SAR, Hong Kong;
(5) Hong Kong Sanatorium and Hospital, Hong Kong; (6) St Paul’s Hospital, Hong Kong; (7) St Teresa’s Hospital, Hong Kong; (8) Hong Kong Baptist Hospital, Hong Kong; (9) Influenza Division, CDC, Atlanta, Georgia, USA; (10) Division of Global Migration and Quarantine, National Center for Preparedness, Detection and Control of Infectious Diseases, CDC, Seattle, Washington, USA.
Abstract:
Background: Non-pharmaceutical interventions are important components in pandemic plans. We conducted a study to investigate whether face masks or improved hand hygiene can prevent influenza transmission among household members.
Methods: We conducted a cluster-randomized trial of households composed of at least 3 members where an index subject presented to an outpatient clinic with influenza-like illness of <48 hours duration. Households of index cases with a positive result on a rapid influenza test were randomized to: (1) control, (2) hand hygiene, or (3) face mask plus hand hygiene interventions. Households were visited within 36 hours of randomization to apply the intervention and after 3 and 6 days to determine secondary infections. The primary outcome was laboratory-confirmed influenza infection by RT-PCR in a household contact.
Results: We recruited 2,750 subjects at outpatient clinics, of whom only 407 tested positive by the rapid test and were randomized. We completed follow-up in 322. Among 306 of these households in which the index case had RT-PCR-confirmed influenza, 75 (8%) household contacts had RT-PCR-confirmed influenza infection during follow-up, with no statistically significant differences in secondary attack ratios between intervention arms (control=10%, hand hygiene=7%, face mask plus hand hygiene=7%; p=0.49). There were statistically significant reductions in secondary attack ratios if interventions were implemented within 48 or 36 hours of symptom onset in the index case (p=0.05, p=0.04, respectively).
Conclusions: Further studies would be needed to confirm small to moderate effect sizes. Interventions may be most effective if implemented soon after index case symptom onset.
