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.