Table 2. Hemagglutination-inhibition responses to 2011–2012 trivalent inactivated influenza vaccine antigens, overall and stratified by age group.
| 2011–2012 Influenza Vaccine Strain | ||||||||
|---|---|---|---|---|---|---|---|---|
| Immunological response measure | H1N1 A/California/07/2009 | H3N2 A/Perth/16/2009 | ||||||
| Overall n = 264 |
Age 50–64 y n = 157 |
Age 65–80 y n = 107 |
*P value |
Overall n = 264 |
Age 50–64 y n = 157 |
Age 65–80 y n = 107 |
*P value |
|
| Seroprotection (HI titer ≥ 1:40) Day 0 (%) | 36.7 | 38.2 | 34.6 | 0.55 | 28.4 | 31.9 | 23.4 | 0.13 |
| Titer ³ 1:40 – Seroprotection Day 21 (%) |
65.9 | 66.9 | 64.5 | 0.69 | 63.3 | 63.7 | 62.6 | 0.86 |
| Seroconversion (4-fold rise at Day 21) (%) | 33.7 | 33.1 | 34.6 | 0.81 | 37.5 | 35.7 | 40.2 | 0.46 |
| GMT ratio (95% CI) | 2.1 (1.9–2.5) |
2.1 (1.8–2.5) |
2.2 (1.8–2.7) |
0.69 | 2.3 (2.0–2.6) |
2.3 (1.9–2.7) |
2.3 (1.9–2.8) |
0.86 |
| Adjusted GMT ratio# (95% CI) | 2.1 (1.9–2.4) |
2.1 (1.8–2.5) |
2.2 (1.8–2.7) |
0.86 | 2.3 (2.0–2.6) |
2.3 (1.9–2.7) |
2.3 (1.9–2.8) |
0.89 |
GMT, geometric mean titer; CI, confidence interval; Seroconversion, 4-fold rise in post vaccination titer; Seroprotected, HI titer ≥ 40. *Comparison of the 2 age groups. #Adjusted for sex, site, race group, and diabetes.