Table 1.

Characteristics of the study subjects (n=1531)

	Smoker (n=321)		Nonsmoker (n=1152)		Rest (n=58)		Total (n=1531)
Subgroup	n	%	n	%	n	%	n
Current vaccination status
Vaccine	153	47.7	590	51.2	28	48.3	771
Placebo	168	52.3	562	48.8	30	51.7	760
Sex
Male	194	60.4	476	41.3	53	91.4	723
Female	127	39.6	676	58.7	5	8.6	808
Age
60–64	170	53.0	482	41.8	16	27.6	668
65–69	100	31.1	326	28.3	19	32.7	445
70–74	42	13.1	231	20.0	11	19.0	284
75–79	9	2.8	71	6.2	8	13.8	88
80–84	0	0.0	31	2.7	3	5.2	34
85–91	0	0.0	11	1.0	1	1.7	12
Diagnosis
Heart	37	11.5	156	13.5	13	22.4	206
Lung	44	13.7	87	7.6	5	8.6	136
Diabetes mellitus	6	1.9	22	1.9	1	1.7	29
Rest	234	72.9	887	77.0	39	67.3	1160
Number with protective titre at pre-titre againsta
A/Singapore/6/86 (H1N1)	3	0.9	6	0.5	2	3.4	11
A/Beijing/353/89 (H3N2)	6	3.3	11	1.0	1	1.7	18
B/Panama/45/90	17	5.3	39	3.4	2	3.4	58
B/Beijing/11/87	23	7.2	71	6.2	3	5.2	97

^aCombinations do not add up to n because subjects without a protective titre are not given.