Table 2.

Sample sizes for a test-negative case-control study design, assuming 80% power to detect an OR=1-VE, by per cent coverage among controls (those testing negative) and number of controls per case, with a two-sided alpha=0.05 test.

Vaccine efficacy (VE; %)	Coverage (% vaccinated among controls)	Sample size (no. of cases) by number of controls per case
		1	2	3	4
90	5	210	171	157	149
	10	103	84	77	73
	20	50	40	37	35
	30	32	26	23	22
	50	19	15	13	12
	70	14	11	9	9
70	5	418	333	303	288
	10	211	167	152	144
	20	107	84	76	72
	30	74	57	52	49
	50	50	38	34	32
	70	46	34	30	28
50	5	962	749	677	641
	10	492	383	345	326
	20	260	201	181	171
	30	186	143	128	120
	50	137	103	92	86
	70	141	105	92	86
30	5	3070	2350	2109	1989
	10	1593	1218	1092	1029
	20	866	659	590	555
	30	638	483	432	406
	50	499	375	334	313
	70	553	412	364	340