Table. Geometric mean titers of antibodies and rates of seroprotection against pandemic (H1N1) 2009 virus before and after seasonal influenza vaccination, by age, Taiwan, 2007–2008*.

Group, age, y	Prevaccination GMT (95% CI)	Prevaccination seroprotection rate, %	Postvaccination GMT (95% CI)	Postvaccination seroprotection rate, %	p value
Children <5, n = 40)
HI	10.4 (9.9–10.9)	0	ND	ND	ND
Adults 20–49, n = 36
HI	12.1 (10.7–13.7)	2.8	12.1 (10.7–13.7)	2.80	NS
MN	26.3 (20.9–32.8)	0	31.7 (25.0–40.3)	0	<0.05
Older adults 50–74, n = 50
HI	16.7 (14.2–19.7)	16	16.7 (14.2–19.7)	16	NS
MN	59.0 (47.7–72.8)	20	74.6 (60.0–92.9)	32	<0.05
Elderly adults >75, n = 50
HI	22.7 (19.5–26.4)	36	23.3 (19.8–27.4)	38	0.159
MN	85.7 (70.8–103.9)	32	107 (89.2–128.5)	44	<0.05
*GMT, geometric mean titer; CI, confidence interval; HI, hemagglutination inhibition; ND, not done; NS, not significant. MN, microneutralization. Mean ± SD ages for the 4 groups were 20.0 ± 11.3 mo for children, 34.5 ± 7.5 y for adults, 65 ± 6 y for older adults, and 79 ± 3.3 y for elderly adults.