Table 2.

Antibody Responses Against Influenza A (H1N1, H3N2) and B for Standard-Dose (SD) and High-Dose (HD) Recipients After Vaccination^a

Viral type	Measure	Time point	SD	HD	P Value
H1N1	GMTs	Prevaccination	43 [39–47]	41 [36–45]	.46
		Week 4	68 [62–75]	111 [98–125]	<.001
		Week 10	55 [50–60]	81 [72–90]	<.001
		Week 20	55 [50–60]	69 [62–77]	.002
	4-fold change (0 to 4 weeks)
		Yes	38 (12%)	103 (34.8%)	<.001
		No	274 (86.7%)	188 (63.5%)
		Missing	4 (1.3%)	5 (1.7%)
H3N2	GMTs	Prevaccination	45 [40–51]	51 [45–58]	.18
		Week 4	123 [108–139]	202 [177–232]	<.001
		Week 10	95 [84–107]	145 [126–167]	<.001
		Week 20	80 [70–90]	117 [103–133]	<.001
	4-fold change (0 to 4 weeks)
		Yes	110 (34.8%)	145 (49%)	<.001
		No	202 (63.9%)	146 (49.3%)
		Missing	4 (1.3%)	5 (1.7%)
B	GMTs	Prevaccination	40 [36–44]	36 [33–39]	.13
		Week 4	67 [60–73]	92 [83–102]	<.001
		Week 10	54 [49–59]	67 [60–74]	.003
		Week 20	51 [46–56]	58 [52–65]	.063
	4-fold change (0 to 4 weeks)
		Yes	39 (12.3%)	89 (30.1%)	<.001
		No	273 (86.4%)	202 (68.2%)
		Missing	4 (1.3%)	5 (1.7%)

Abbreviations: GMTs, geometric mean titers.

^aFor the calculation and comparison of GMTs, participants that developed influenza were removed; GMTs are reported as mean [95% confidence interval], and significance (P) was determined by t test. For 4-fold change, the count (frequency) of participants that exhibited a 4-fold or more increase in antibody titers from prevaccination (week 0) to 4 weeks postvaccination is reported; significance was determined by χ ² test.