Table 1. Open in new tab HI Antibody...

Season	Vaccinees, No.	Virus	HA Group	Amino Acid	GMT	HI Titer ≥40, %	Seroconversion, %^a	LRs, No. (%)^b
2010–2011	50	X-179A	NA	K	R	17	394 (40–1280)	36	100	90	NA
		RG-K163	NA	K	Q	17	260^c (20–1280)	40	98	86	7 (14)
		RG-K163Q	NA	Q	Q	13	143^c,d (5–1280)	24	86	80	18 (36)^d
		MI/15e	6B.1	Q	R	12	229^c (5–1280)	22	94	82	9 (18)
		MI/15c	6B.1	Q	Q	11	125^c,e (5–1280)	20	84	82	20 (40)^e
		IW/15e	6B.2	Q	R	11	181^c (5–1280)	14	92	88	10 (20)
		IW/15c	6B.2	Q	Q	10	112^c,e (5–1280)	12	80	84	19 (38)
2011–2012	54	X-179A	NA	K	R	27	281 (40–1280)	46	100	72	NA
		RG-K163	NA	K	Q	20	156^c (40–640)	35	100	69	9 (17)
		RG-K163Q	NA	Q	Q	16	106^c,d (5–640)	31	87	69	19 (35)^d
		MI/15e	6B.1	Q	R	21	207^c (5–1280)	35	98	72	7 (13)
		MI/15c	6B.1	Q	Q	22	166^c (5–1280)	35	89	69	15 (28)
		IW/15e	6B.2	Q	R	19	139^c (5–1280)	37	94	72	8 (15)
		IW/15c	6B.2	Q	Q	19	110^c (5–640)	33	80	72	20 (37)^e
2013–2014	42	X-179A	NA	K	R	17	242 (40–1280)	29	100	83	NA
		RG-K163	NA	K	Q	16	189^c (20–1280)	31	98	79	7 (17)
		RG-K163Q	NA	Q	Q	12	108^c,d (10–640)	21	86	74	12 (29)
		MI/15e	6B.1	Q	R	20	242 (10–1280)	43	98	76	4 (10)
		MI/15c	6B.1	Q	Q	14	119^c,e (5–1280)	24	83	69	12 (29)^e
		IW/15e	6B.2	Q	R	13	125^c (5–640)	24	90	74	5 (12)
		IW/15c	6B.2	Q	Q	11	72^c,e (5–640)	17	76	62	17 (40)^e
2014–2015	61	X-179A	NA	K	R	30	286 (40–1280)	49	100	77	NA
		RG-K163	NA	K	Q	30	220^c (5–1280)	57	98	74	4 (7)
		RG-K163Q	NA	Q	Q	25	164^c,d (5–1280)	49	93	70	9 (15)
		MI/15e	6B.1	Q	R	31	264 (10–1280)	51	98	75	2 (3)
		MI/15c	6B.1	Q	Q	24	188^c,e (5–1280)	46	92	74	10 (16)^e
		IW/15e	6B.2	Q	R	20	173^c (5–1280)	39	95	72	4 (7)
		IW/15c	6B.2	Q	Q	20	140^c (5–1280)	41	89	67	16 (25)^e
2015–2016	60	X-179A	NA	K	R	50	214 (40–1280)	68	100	42	NA
		RG-K163	NA	K	Q	53	188^c (40–1280)	72	100	40	1 (2)
		RG-K163Q	NA	Q	Q	46	156^c,d (5–1280)	70	97	38	2 (3)
		MI/15e	6B.1	Q	R	55	221 (10–1280)	68	98	43	1 (2)
		MI/15c	6B.1	Q	Q	50	192 (5–1280)	68	97	42	2 (3)
		IW/15e	6B.2	Q	R	33	117^c (5–1280)	60	98	38	4 (7)
		IW/15c	6B.2	Q	Q	34	117^c (5–1280)	57	97	40	9 (15)
2016–2017	33	X-179A	NA	K	R	77	244 (40–1280)	85	100	30	NA
		RG-K163	NA	K	Q	58	224 (40–1280)	73	100	36	0
		RG-K163Q	NA	Q	Q	46	144^c,d (5–1280)	70	97	33	4 (12)
		MI/15e	6B.1	Q	R	56	181^c (5–1280)	76	97	39	4 (12)
		MI/15c	6B.1	Q	Q	43	138^c,e (5–1280)	64	82	36	6 (18)
		IW/15e	6B.2	Q	R	48	160^c (5–1280)	73	94	33	4 (13)
		IW/15c	6B.2	Q	Q	47	160^c (5–1280)	67	97	36	5 (15)
Total	300	X-179A	NA	K	R	30	272 (40–1280)	51	100	67	NA
		RG-K163	NA	K	Q	28	202^c (5–1280)	51	99	64	28 (9)
		RG-K163Q	NA	Q	Q	23	136^c,d (5–1280)	44	91	62	64 (21)^d
		MI/15e	6B.1	Q	R	28	226^c (5–1280)	48	98	66	27 (9)
		MI/15c	6B.1	Q	Q	24	156^c,e (5–1280)	43	89	63	65 (22)^e
		IW/15e	6B.2	Q	R	20	147^c (5–1280)	40	94	64	35 (12)
		IW/15c	6B.2	Q	Q	20	115^c,e (5–1280)	37	87	61	76 (25%)^e

Season

Vaccinees, No.

Virus

HA
Group

Amino Acid

GMT

HI Titer ≥40, %

Seroconversion, %^a

LRs, No. (%)^b

163

223

Pre

Post (Range)

Pre

Post

2010–2011

X-179A

394 (40–1280)

100

RG-K163

260^c (20–1280)

7 (14)

RG-K163Q

143^c,d (5–1280)

18 (36)^d

MI/15e

6B.1

229^c (5–1280)

9 (18)

MI/15c

6B.1

125^c,e (5–1280)

20 (40)^e

IW/15e

6B.2

181^c (5–1280)

10 (20)

IW/15c

6B.2

112^c,e (5–1280)

19 (38)

2011–2012

X-179A

281 (40–1280)

100

RG-K163

156^c (40–640)

100

9 (17)

RG-K163Q

106^c,d (5–640)

19 (35)^d

MI/15e

6B.1

207^c (5–1280)

7 (13)

MI/15c

6B.1

166^c (5–1280)

15 (28)

IW/15e

6B.2

139^c (5–1280)

8 (15)

IW/15c

6B.2

110^c (5–640)

20 (37)^e

2013–2014

X-179A

242 (40–1280)

100

RG-K163

189^c (20–1280)

7 (17)

RG-K163Q

108^c,d (10–640)

12 (29)

MI/15e

6B.1

242 (10–1280)

4 (10)

MI/15c

6B.1

119^c,e (5–1280)

12 (29)^e

IW/15e

6B.2

125^c (5–640)

5 (12)

IW/15c

6B.2

72^c,e (5–640)

17 (40)^e

2014–2015

X-179A

286 (40–1280)

100

RG-K163

220^c (5–1280)

4 (7)

RG-K163Q

164^c,d (5–1280)

9 (15)

MI/15e

6B.1

264 (10–1280)

2 (3)

MI/15c

6B.1

188^c,e (5–1280)

10 (16)^e

IW/15e

6B.2

173^c (5–1280)

4 (7)

IW/15c

6B.2

140^c (5–1280)

16 (25)^e

2015–2016

X-179A

214 (40–1280)

100

RG-K163

188^c (40–1280)

100

1 (2)

RG-K163Q

156^c,d (5–1280)

2 (3)

MI/15e

6B.1

221 (10–1280)

1 (2)

MI/15c

6B.1

192 (5–1280)

2 (3)

IW/15e

6B.2

117^c (5–1280)

4 (7)

IW/15c

6B.2

117^c (5–1280)

9 (15)

2016–2017

X-179A

244 (40–1280)

100

RG-K163

224 (40–1280)

100

RG-K163Q

144^c,d (5–1280)

4 (12)

MI/15e

6B.1

181^c (5–1280)

4 (12)

MI/15c

6B.1

138^c,e (5–1280)

6 (18)

IW/15e

6B.2

160^c (5–1280)

4 (13)

IW/15c

6B.2

160^c (5–1280)

5 (15)

Total

300

X-179A

272 (40–1280)

100

RG-K163

202^c (5–1280)

28 (9)

RG-K163Q

136^c,d (5–1280)

64 (21)^d

MI/15e

6B.1

226^c (5–1280)

27 (9)

MI/15c

6B.1

156^c,e (5–1280)

65 (22)^e

IW/15e

6B.2

147^c (5–1280)

35 (12)

IW/15c

6B.2

115^c,e (5–1280)

76 (25%)^e

Season	Vaccinees, No.	Virus	HA Group	Amino Acid	GMT	HI Titer ≥40, %	Seroconversion, %^a	LRs, No. (%)^b
2010–2011	50	X-179A	NA	K	R	17	394 (40–1280)	36	100	90	NA
		RG-K163	NA	K	Q	17	260^c (20–1280)	40	98	86	7 (14)
		RG-K163Q	NA	Q	Q	13	143^c,d (5–1280)	24	86	80	18 (36)^d
		MI/15e	6B.1	Q	R	12	229^c (5–1280)	22	94	82	9 (18)
		MI/15c	6B.1	Q	Q	11	125^c,e (5–1280)	20	84	82	20 (40)^e
		IW/15e	6B.2	Q	R	11	181^c (5–1280)	14	92	88	10 (20)
		IW/15c	6B.2	Q	Q	10	112^c,e (5–1280)	12	80	84	19 (38)
2011–2012	54	X-179A	NA	K	R	27	281 (40–1280)	46	100	72	NA
		RG-K163	NA	K	Q	20	156^c (40–640)	35	100	69	9 (17)
		RG-K163Q	NA	Q	Q	16	106^c,d (5–640)	31	87	69	19 (35)^d
		MI/15e	6B.1	Q	R	21	207^c (5–1280)	35	98	72	7 (13)
		MI/15c	6B.1	Q	Q	22	166^c (5–1280)	35	89	69	15 (28)
		IW/15e	6B.2	Q	R	19	139^c (5–1280)	37	94	72	8 (15)
		IW/15c	6B.2	Q	Q	19	110^c (5–640)	33	80	72	20 (37)^e
2013–2014	42	X-179A	NA	K	R	17	242 (40–1280)	29	100	83	NA
		RG-K163	NA	K	Q	16	189^c (20–1280)	31	98	79	7 (17)
		RG-K163Q	NA	Q	Q	12	108^c,d (10–640)	21	86	74	12 (29)
		MI/15e	6B.1	Q	R	20	242 (10–1280)	43	98	76	4 (10)
		MI/15c	6B.1	Q	Q	14	119^c,e (5–1280)	24	83	69	12 (29)^e
		IW/15e	6B.2	Q	R	13	125^c (5–640)	24	90	74	5 (12)
		IW/15c	6B.2	Q	Q	11	72^c,e (5–640)	17	76	62	17 (40)^e
2014–2015	61	X-179A	NA	K	R	30	286 (40–1280)	49	100	77	NA
		RG-K163	NA	K	Q	30	220^c (5–1280)	57	98	74	4 (7)
		RG-K163Q	NA	Q	Q	25	164^c,d (5–1280)	49	93	70	9 (15)
		MI/15e	6B.1	Q	R	31	264 (10–1280)	51	98	75	2 (3)
		MI/15c	6B.1	Q	Q	24	188^c,e (5–1280)	46	92	74	10 (16)^e
		IW/15e	6B.2	Q	R	20	173^c (5–1280)	39	95	72	4 (7)
		IW/15c	6B.2	Q	Q	20	140^c (5–1280)	41	89	67	16 (25)^e
2015–2016	60	X-179A	NA	K	R	50	214 (40–1280)	68	100	42	NA
		RG-K163	NA	K	Q	53	188^c (40–1280)	72	100	40	1 (2)
		RG-K163Q	NA	Q	Q	46	156^c,d (5–1280)	70	97	38	2 (3)
		MI/15e	6B.1	Q	R	55	221 (10–1280)	68	98	43	1 (2)
		MI/15c	6B.1	Q	Q	50	192 (5–1280)	68	97	42	2 (3)
		IW/15e	6B.2	Q	R	33	117^c (5–1280)	60	98	38	4 (7)
		IW/15c	6B.2	Q	Q	34	117^c (5–1280)	57	97	40	9 (15)
2016–2017	33	X-179A	NA	K	R	77	244 (40–1280)	85	100	30	NA
		RG-K163	NA	K	Q	58	224 (40–1280)	73	100	36	0
		RG-K163Q	NA	Q	Q	46	144^c,d (5–1280)	70	97	33	4 (12)
		MI/15e	6B.1	Q	R	56	181^c (5–1280)	76	97	39	4 (12)
		MI/15c	6B.1	Q	Q	43	138^c,e (5–1280)	64	82	36	6 (18)
		IW/15e	6B.2	Q	R	48	160^c (5–1280)	73	94	33	4 (13)
		IW/15c	6B.2	Q	Q	47	160^c (5–1280)	67	97	36	5 (15)
Total	300	X-179A	NA	K	R	30	272 (40–1280)	51	100	67	NA
		RG-K163	NA	K	Q	28	202^c (5–1280)	51	99	64	28 (9)
		RG-K163Q	NA	Q	Q	23	136^c,d (5–1280)	44	91	62	64 (21)^d
		MI/15e	6B.1	Q	R	28	226^c (5–1280)	48	98	66	27 (9)
		MI/15c	6B.1	Q	Q	24	156^c,e (5–1280)	43	89	63	65 (22)^e
		IW/15e	6B.2	Q	R	20	147^c (5–1280)	40	94	64	35 (12)
		IW/15c	6B.2	Q	Q	20	115^c,e (5–1280)	37	87	61	76 (25%)^e

Table 1.

Open in new tab

HI Antibody Responses Against Influenza A(H1N1)pdm09 Viruses in Adults After Vaccination

Season	Vaccinees, No.	Virus	HA Group	Amino Acid		GMT		HI Titer ≥40, %		Seroconversion, %^a	LRs, No. (%)^b
Season	Vaccinees, No.	Virus	HA Group	163	223	Pre	Post (Range)	Pre	Post
2010–2011	50	X-179A	NA	K	R	17	394 (40–1280)	36	100	90	NA
		RG-K163	NA	K	Q	17	260^c (20–1280)	40	98	86	7 (14)
		RG-K163Q	NA	Q	Q	13	143^c,d (5–1280)	24	86	80	18 (36)^d
		MI/15e	6B.1	Q	R	12	229^c (5–1280)	22	94	82	9 (18)
		MI/15c	6B.1	Q	Q	11	125^c,e (5–1280)	20	84	82	20 (40)^e
		IW/15e	6B.2	Q	R	11	181^c (5–1280)	14	92	88	10 (20)
		IW/15c	6B.2	Q	Q	10	112^c,e (5–1280)	12	80	84	19 (38)
2011–2012	54	X-179A	NA	K	R	27	281 (40–1280)	46	100	72	NA
		RG-K163	NA	K	Q	20	156^c (40–640)	35	100	69	9 (17)
		RG-K163Q	NA	Q	Q	16	106^c,d (5–640)	31	87	69	19 (35)^d
		MI/15e	6B.1	Q	R	21	207^c (5–1280)	35	98	72	7 (13)
		MI/15c	6B.1	Q	Q	22	166^c (5–1280)	35	89	69	15 (28)
		IW/15e	6B.2	Q	R	19	139^c (5–1280)	37	94	72	8 (15)
		IW/15c	6B.2	Q	Q	19	110^c (5–640)	33	80	72	20 (37)^e
2013–2014	42	X-179A	NA	K	R	17	242 (40–1280)	29	100	83	NA
		RG-K163	NA	K	Q	16	189^c (20–1280)	31	98	79	7 (17)
		RG-K163Q	NA	Q	Q	12	108^c,d (10–640)	21	86	74	12 (29)
		MI/15e	6B.1	Q	R	20	242 (10–1280)	43	98	76	4 (10)
		MI/15c	6B.1	Q	Q	14	119^c,e (5–1280)	24	83	69	12 (29)^e
		IW/15e	6B.2	Q	R	13	125^c (5–640)	24	90	74	5 (12)
		IW/15c	6B.2	Q	Q	11	72^c,e (5–640)	17	76	62	17 (40)^e
2014–2015	61	X-179A	NA	K	R	30	286 (40–1280)	49	100	77	NA
		RG-K163	NA	K	Q	30	220^c (5–1280)	57	98	74	4 (7)
		RG-K163Q	NA	Q	Q	25	164^c,d (5–1280)	49	93	70	9 (15)
		MI/15e	6B.1	Q	R	31	264 (10–1280)	51	98	75	2 (3)
		MI/15c	6B.1	Q	Q	24	188^c,e (5–1280)	46	92	74	10 (16)^e
		IW/15e	6B.2	Q	R	20	173^c (5–1280)	39	95	72	4 (7)
		IW/15c	6B.2	Q	Q	20	140^c (5–1280)	41	89	67	16 (25)^e
2015–2016	60	X-179A	NA	K	R	50	214 (40–1280)	68	100	42	NA
		RG-K163	NA	K	Q	53	188^c (40–1280)	72	100	40	1 (2)
		RG-K163Q	NA	Q	Q	46	156^c,d (5–1280)	70	97	38	2 (3)
		MI/15e	6B.1	Q	R	55	221 (10–1280)	68	98	43	1 (2)
		MI/15c	6B.1	Q	Q	50	192 (5–1280)	68	97	42	2 (3)
		IW/15e	6B.2	Q	R	33	117^c (5–1280)	60	98	38	4 (7)
		IW/15c	6B.2	Q	Q	34	117^c (5–1280)	57	97	40	9 (15)
2016–2017	33	X-179A	NA	K	R	77	244 (40–1280)	85	100	30	NA
		RG-K163	NA	K	Q	58	224 (40–1280)	73	100	36	0
		RG-K163Q	NA	Q	Q	46	144^c,d (5–1280)	70	97	33	4 (12)
		MI/15e	6B.1	Q	R	56	181^c (5–1280)	76	97	39	4 (12)
		MI/15c	6B.1	Q	Q	43	138^c,e (5–1280)	64	82	36	6 (18)
		IW/15e	6B.2	Q	R	48	160^c (5–1280)	73	94	33	4 (13)
		IW/15c	6B.2	Q	Q	47	160^c (5–1280)	67	97	36	5 (15)
Total	300	X-179A	NA	K	R	30	272 (40–1280)	51	100	67	NA
		RG-K163	NA	K	Q	28	202^c (5–1280)	51	99	64	28 (9)
		RG-K163Q	NA	Q	Q	23	136^c,d (5–1280)	44	91	62	64 (21)^d
		MI/15e	6B.1	Q	R	28	226^c (5–1280)	48	98	66	27 (9)
		MI/15c	6B.1	Q	Q	24	156^c,e (5–1280)	43	89	63	65 (22)^e
		IW/15e	6B.2	Q	R	20	147^c (5–1280)	40	94	64	35 (12)
		IW/15c	6B.2	Q	Q	20	115^c,e (5–1280)	37	87	61	76 (25%)^e

Season	Vaccinees, No.	Virus	HA Group	Amino Acid		GMT		HI Titer ≥40, %		Seroconversion, %^a	LRs, No. (%)^b
Season	Vaccinees, No.	Virus	HA Group	163	223	Pre	Post (Range)	Pre	Post
2010–2011	50	X-179A	NA	K	R	17	394 (40–1280)	36	100	90	NA
		RG-K163	NA	K	Q	17	260^c (20–1280)	40	98	86	7 (14)
		RG-K163Q	NA	Q	Q	13	143^c,d (5–1280)	24	86	80	18 (36)^d
		MI/15e	6B.1	Q	R	12	229^c (5–1280)	22	94	82	9 (18)
		MI/15c	6B.1	Q	Q	11	125^c,e (5–1280)	20	84	82	20 (40)^e
		IW/15e	6B.2	Q	R	11	181^c (5–1280)	14	92	88	10 (20)
		IW/15c	6B.2	Q	Q	10	112^c,e (5–1280)	12	80	84	19 (38)
2011–2012	54	X-179A	NA	K	R	27	281 (40–1280)	46	100	72	NA
		RG-K163	NA	K	Q	20	156^c (40–640)	35	100	69	9 (17)
		RG-K163Q	NA	Q	Q	16	106^c,d (5–640)	31	87	69	19 (35)^d
		MI/15e	6B.1	Q	R	21	207^c (5–1280)	35	98	72	7 (13)
		MI/15c	6B.1	Q	Q	22	166^c (5–1280)	35	89	69	15 (28)
		IW/15e	6B.2	Q	R	19	139^c (5–1280)	37	94	72	8 (15)
		IW/15c	6B.2	Q	Q	19	110^c (5–640)	33	80	72	20 (37)^e
2013–2014	42	X-179A	NA	K	R	17	242 (40–1280)	29	100	83	NA
		RG-K163	NA	K	Q	16	189^c (20–1280)	31	98	79	7 (17)
		RG-K163Q	NA	Q	Q	12	108^c,d (10–640)	21	86	74	12 (29)
		MI/15e	6B.1	Q	R	20	242 (10–1280)	43	98	76	4 (10)
		MI/15c	6B.1	Q	Q	14	119^c,e (5–1280)	24	83	69	12 (29)^e
		IW/15e	6B.2	Q	R	13	125^c (5–640)	24	90	74	5 (12)
		IW/15c	6B.2	Q	Q	11	72^c,e (5–640)	17	76	62	17 (40)^e
2014–2015	61	X-179A	NA	K	R	30	286 (40–1280)	49	100	77	NA
		RG-K163	NA	K	Q	30	220^c (5–1280)	57	98	74	4 (7)
		RG-K163Q	NA	Q	Q	25	164^c,d (5–1280)	49	93	70	9 (15)
		MI/15e	6B.1	Q	R	31	264 (10–1280)	51	98	75	2 (3)
		MI/15c	6B.1	Q	Q	24	188^c,e (5–1280)	46	92	74	10 (16)^e
		IW/15e	6B.2	Q	R	20	173^c (5–1280)	39	95	72	4 (7)
		IW/15c	6B.2	Q	Q	20	140^c (5–1280)	41	89	67	16 (25)^e
2015–2016	60	X-179A	NA	K	R	50	214 (40–1280)	68	100	42	NA
		RG-K163	NA	K	Q	53	188^c (40–1280)	72	100	40	1 (2)
		RG-K163Q	NA	Q	Q	46	156^c,d (5–1280)	70	97	38	2 (3)
		MI/15e	6B.1	Q	R	55	221 (10–1280)	68	98	43	1 (2)
		MI/15c	6B.1	Q	Q	50	192 (5–1280)	68	97	42	2 (3)
		IW/15e	6B.2	Q	R	33	117^c (5–1280)	60	98	38	4 (7)
		IW/15c	6B.2	Q	Q	34	117^c (5–1280)	57	97	40	9 (15)
2016–2017	33	X-179A	NA	K	R	77	244 (40–1280)	85	100	30	NA
		RG-K163	NA	K	Q	58	224 (40–1280)	73	100	36	0
		RG-K163Q	NA	Q	Q	46	144^c,d (5–1280)	70	97	33	4 (12)
		MI/15e	6B.1	Q	R	56	181^c (5–1280)	76	97	39	4 (12)
		MI/15c	6B.1	Q	Q	43	138^c,e (5–1280)	64	82	36	6 (18)
		IW/15e	6B.2	Q	R	48	160^c (5–1280)	73	94	33	4 (13)
		IW/15c	6B.2	Q	Q	47	160^c (5–1280)	67	97	36	5 (15)
Total	300	X-179A	NA	K	R	30	272 (40–1280)	51	100	67	NA
		RG-K163	NA	K	Q	28	202^c (5–1280)	51	99	64	28 (9)
		RG-K163Q	NA	Q	Q	23	136^c,d (5–1280)	44	91	62	64 (21)^d
		MI/15e	6B.1	Q	R	28	226^c (5–1280)	48	98	66	27 (9)
		MI/15c	6B.1	Q	Q	24	156^c,e (5–1280)	43	89	63	65 (22)^e
		IW/15e	6B.2	Q	R	20	147^c (5–1280)	40	94	64	35 (12)
		IW/15c	6B.2	Q	Q	20	115^c,e (5–1280)	37	87	61	76 (25%)^e

Abbreviations: GMTs, geometric mean titers; HA, hemagglutinin; HI, hemagglutination inhibition; IW/15, A/Iowa/53/2015 field strain grown in egg (IW/15e) or Madin-Darby canine kidney cells (IW/15c); LRs, low responders; MI/15, A/Michigan/45/2015 field strain grown in egg (MI/15e) or Madin-Darby canine kidney cells (MI/15c); NA, not applicable; Post, postvaccination; Pre, prevaccination; RG-K163, A/California/8/2009-PR8 egg-grown virus possessing HA-K163; RG-K163Q, RG-CA egg-grown virus engineered to possess HA-K163Q mutation; X-179A, A/California/7/2009-PR8 egg-grown vaccine virus. Response to vaccine virus X-179A are in bold.

^aPercentage of seroconversion, defined as ≥4-fold increase from prevaccination to postvaccination titers, where the postvaccination titer is ≥40.

^bLow responders defined as those with ≥4-fold reduced postvaccination HI antibody titers to the corresponding virus compared with X-179A.

^cP < .05 for RG-CA viruses and 2015 field strains vs X-179A vaccine strain.

^dP < .05 for RG-K163Q vs RG-K163 virus.

^eP < .05 for MI/15 and IW/15 cell-grown viruses vs their paired egg-grown viruses with an egg-adapted mutation (Q223R).

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