Table 1.
Baseline Characteristics of the 1247 Study Participants during the 2004–2005 Influenza Season in Michigan.*
| Live Attenuated Vaccine Group | Inactivated Vaccine Group | Placebo Group | Total | |
|---|---|---|---|---|
| Characteristic | (N = 519) | (N = 522) | (N = 206) | (N = 1247) |
| Percentage of participants | 41.6 | 41.9 | 16.5 | 100 |
| Mean age — yr | 26.3±9.0 | 27.2±9.4 | 27.8±9.9 | 26.9±9.3 |
| Age category — no. (%) | ||||
| 18–19 yr | 162 (31.2) | 156 (29.9) | 64 (31.1) | 382 (30.6) |
| 20–24 yr | 151 (29.1) | 129 (24.7) | 49 (23.8) | 329 (26.4) |
| 25–34 yr | 83 (16.0) | 96 (18.4) | 30 (14.6) | 209 (16.8) |
| 35–46 yr | 123 (23.7) | 141 (27.0) | 63 (30.6) | 327 (26.2) |
| Sex — no. (%) | ||||
| Women | 313 (60.3) | 334 (64.0) | 128 (62.1) | 775 (62.1) |
| Men | 206 (39.7) | 188 (36.0) | 78 (37.9) | 472 (37.9) |
| Race or ethnic group — no. (%)† | ||||
| White | 444 (85.5) | 452 (86.6) | 179 (86.9) | 1075 (86.2) |
| Nonwhite | 75 (14.5) | 70 (13.4) | 27 (13.1) | 172 (13.8) |
| Prior receipt of influenza vaccine — no. (%) | 265 (51.1) | 263 (50.4) | 100 (48.5) | 628 (50.4) |
*
Plus–minus values are means ±SD. Placebo was physiologic saline administered as either an intramuscular injection (103 participants) or an intranasal spray (103 participants). For the purposes of efficacy analyses, both placebos were considered equivalent and were combined.
†
Race or ethnic group was self-reported. “Nonwhite” included black, Asian, Hispanic, and other or mixed.