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Volume 15, Number 3—March 2009

Perspective

Meeting the Challenge of Influenza Pandemic Preparedness in Developing Countries

David S. FedsonComments to Author 
Author affiliation: University of Virginia, Charlottesville, Virginia, USA (retired)

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Table 4

Sample size requirements for a randomized controlled trial of treatment to reduce deaths in a pandemic caused by a subtype H5N1-like influenza*

Case-fatality rate, %
Reduction in no. deaths, % Total sample size (power)
Untreated Treated 80% 90% 95%
50 37.5 25 530 690 850
50 25 50 140 170 210
50 12.5 75 60 80 90

*1:1 randomization of persons to the 2 treatment groups, α = 0.05 (2-sided), χ2 test (continuity corrected). The example shown assumes a case-fatality rate of 50%, which is similar to what has been seen for patients infected with influenza virus A (H5N1). If a new pandemic virus is associated with a lower case-fatality rate, sample sizes required to show similar reductions in case-fatality rates would have to be larger.

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