Table 1.
Characteristics of Subjects Included in Analysis Set by Intervention
| Intervention |
P Value | Total (N = 941) | |||
|---|---|---|---|---|---|
| IIV (N = 431) | LAIV (N = 381) | Placebo (N = 129) | |||
| Percentage of participants | 45.8 | 40.5 | 13.7 | 100 | |
| Mean age, y ± SD | 25.9 ± 9.1 | 25.1 ± 8.6 | 26.1 ± 9.6 | .47a | 25.6 ± 8.9 |
| Age category, N (%) | |||||
| 18–19 y | 128 (29.7) | 121 (31.8) | 45 (34.9) | .37b | 294 (31.2) |
| 20–24 y | 166 (38.5) | 154 (40.4) | 44 (34.1) | 364 (38.7) | |
| 25–34 y | 51 (11.8) | 40 (10.5) | 9 (7.0) | 100 (10.6) | |
| 35–48 y | 86 (20.0) | 66 (17.3) | 31 (24.0) | 183 (19.5) | |
| Sex, N (%) | |||||
| Female | 271 (62.9) | 243 (63.8) | 77 (59.7) | .71b | 591 (62.8) |
| Male | 160 (37.1) | 138 (36.2) | 52 (40.3) | 350 (37.2) | |
| Race, N (%) | |||||
| White | 374 (86.8) | 333 (87.4) | 115 (89.1) | .78b | 822 (87.4) |
| Nonwhite | 57 (13.2) | 48 (12.6) | 14 (10.9) | 119 (12.6) | |
| Participated in 2004–2005, N (%)c | |||||
| Yes | 194 (45.0) | 185 (48.6) | 63 (48.8) | .54b | 442 (47.0) |
| No | 237 (55.0) | 196 (51.4) | 66 (51.2) | 499 (53.0) | |
| Standardized results, N (%) | |||||
| Yes | 187 (43.4) | 173 (45.4) | 45 (34.9) | .11b | 405 (43.0) |
| No | 244 (56.6) | 208 (54.6) | 84 (65.1) | 536 (57.0) | |
Abbreviations: IIV, inactivated influenza vaccine; LAIV, live attenuated influenza vaccine.
a Kruskal–Wallis test.
b χ2 test.
c Participation in the 2004–2005 study year is used as a proxy for 2004–2005 vaccination status. Those enrolled in both 2004–2005 and 2005–2006 received the same intervention both years; however, history of vaccination in the 2004–2005 season was not explicitly determined for those newly enrolled in 2005–2006.