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J Antimicrob Chemother. 2014 May;69(5):1397-406. doi: 10.1093/jac/dkt496. Epub 2013 Dec 16.

Effectiveness of neuraminidase inhibitors in preventing hospitalization during the H1N1 influenza pandemic in British Columbia, Canada.

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University of British Columbia, Vancouver, BC, Canada.



In British Columbia (BC), Canada, neuraminidase inhibitors (NIs) were publicly funded during the 2009 A(H1N1)pdm09 pandemic for treatment of high-risk patients and/or anyone with moderate-to-severe illness. We assessed antiviral effectiveness (AVE) against hospitalization in that context.


A population-based cohort study was conducted using linked administrative data. The cohort included all individuals living in BC during the study period (1 September to 31 December 2009) with a diagnostic code consistent with influenza or pandemic H1N1. The main study period pertained to the second-wave A(H1N1)pdm09 circulation (1 October to 31 December 2009), with sensitivity analyses around the more specific pandemic peak (18 October to 7 November). Exposure was defined by same-day NI prescription. The main outcome was all-cause hospitalization within 14 days of the outpatient influenza diagnosis. Cox proportional hazards models assessed AVE with 1 : 1 propensity-score matching and covariate adjustment.


After matching, there were 304/58,061 NI-exposed and 345/58,061 unexposed patients hospitalized during the main study period. The very young [<6 months (35.0; 95% CI 16.7-73.4)], the old [65-79 years (13.7; 95% CI 10.1-18.6)] and the very old [≥80 years (38.7; 95% CI 26.6-56.5)] had the highest hospitalization rate per 1000 patients overall. Fully adjusted AVE against all-cause hospitalization during the main study period was 16% (95% CI 2%-28%), similar to the pandemic peak (15%; 95% CI -4%-30%).


The use of NIs was associated with modest protection against hospitalization during the 2009 pandemic, but appeared underutilized in affected age groups with the highest hospitalization risk.


antivirals; cohort; mortality; oseltamivir; population-based; zanamivir

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