Volume 15, Number 3—March 2009
Perspective
Meeting the Challenge of Influenza Pandemic Preparedness in Developing Countries
David S. Fedson
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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