Table 1.

Bias of Estimates and Coverage Probabilities of Wald-Based 95% Confidence Intervals for SCE(t) With t = 24 Months

		Bias		Coverage probability
VE	β	Mean	Median	Bootstrap	Analytic
~.3	.1	−.002	0	.946	.948
	.2	−.007	−.007	.943	.949
	1	−.006	−.003	.943	.946
	∞	−.007	.005	.948	.953
~.6	.1	.003	.006	.939	.940
	.2	.013	.015	.945	.945
	1	.042	.020	.933	.912
	∞	.035	0	.935

NOTE: Analytic coverage probabilities when VE ≈ .6, β = ∞ are not given, because in many simulations there were no failures in the vaccine arm.