Table 2 Immunogenicity of IIV4 by young (< 65 years) and old (≥ 65 years) age groups

H1N1

17.81 (15.51–20.44)

91.74 (73.72–114.18)

5.15 (4.23–6.28)

53.89 (46.02–61.62)

25.75 (19.30–33.08)

76.05 (68.84–82.30)

 < 65 years

20.00 (16.34–24.48)

131.91 (94.07–184.98)

6.60 (4.90–8.88)

60.76 (49.13–71.56)

25.32 (16.20–36.36)

81.01 (70.62–88.97)

 ≥ 65 years

16.04 (13.27–19.39)

66.22 (50.47–86.88)

4.13 (3.18–5.36)

47.73 (36.96–58.65)

26.14 (17.34–36.59)

71.59 (60.98–80.70)

P

0.117

0.002

0.018

0.092

0.904

0.154

H3N2

12.93 (11.35–14.74)

58.36 (50.29–67.72)

4.51 (3.77–5.4)

53.89 (46.02–61.62)

16.77 (11.44–23.31)

79.64 (72.73–85.47)

 < 65 years

14.46 (11.93–17.52)

58.85 (47.13–73.48)

4.07 (3.14–5.28)

53.16 (41.60–64.49)

16.46 (9.06–26.49)

82.28 (72.06–89.96)

 ≥ 65 years

11.71 (9.79–14.00)

57.92 (47.23–71.03)

4.95 (3.84–6.38)

54.55 (43.58–65.20)

17.05 (9.87–26.55)

77.27 (67.11–85.53)

P

0.097

0.574

0.269

0.858

0.919

0.423

B/Victoria

15.27 (13.41–17.39)

76.43 (65–89.87)

5 (4.33–5.78)

66.47 (58.76–73.58)

20.36 (14.53–27.27)

83.23 (76.69–88.56)

 < 65 years

17.08 (14.51–20.10)

87.34 (71.22–107.11)

5.11 (4.17–6.27)

72.15 (60.93–81.65)

17.72 (10.04–27.94)

89.87 (81.02–95.53)

 ≥ 65 years

13.81 (11.32–16.85)

67.80 (52.91–86.88)

4.91 (3.99–6.04)

61.36 (50.38–71.56)

22.73 (14.47–32.89)

77.27 (67.11–85.53)

P

0.065

0.05

0.515

0.14

0.423

0.03

B/Yamagata

30.8 (26.46–35.85)

147.25 (125.05–173.41)

4.78 (4.02–5.68)

64.07 (56.30–71.34)

62.87 (55.07–70.21)

94.61 (90.02–97.51)

 < 65 years

44.44 (36.31–54.40)

187.37 (155.07–226.41)

4.22 (3.25–5.47)

56.96 (45.33–68.06)

77.22 (66.40–85.90)

100.00 (95.44–100.00)

 ≥ 65 years

22.16 (18.08–27.16)

118.61 (91.95–153.01)

5.35 (4.25–6.75)

70.45 (59.78–79.71)

50.00 (39.15–60.85)

89.77 (81.47–95.22)

P

 < 0.001

0.012

0.131

0.07

 < 0.001

0.003