Table 1.
Participant baseline characteristics.
| Characteristic | IIV4 lot 1 | IIV4 lot 2 | IIV4 lot 3 | IIV3-1 | IIV3-2 |
|---|---|---|---|---|---|
| Randomized, N | |||||
| Total | 554 | 555 | 561 | 279 | 276 |
| Younger adults (18–60 y) | 278 | 277 | 281 | 140 | 138 |
| Older adults (>60 y) | 276 | 278 | 280 | 139 | 138 |
| Age (y), mean ± standard deviation | 54.5 ± 18.1 | 54.8 ± 18.2 | 54.5 ± 18.1 | 55.6 ± 16.9 | 53.7 ±18.6 |
| Sex, n (%) | |||||
| Male | 244 (44.1) | 251 (45.2) | 276 (49.5) | 126 (45.3) | 124 (45.1) |
| Female | 309 (55.9) | 304 (54.8) | 282 (50.5) | 152 (54.7) | 151 (54.9) |
| Ethnicity, n(%) | |||||
| White/Caucasian | 551 (99.6) | 548 (98.7) | 555 (99.5) | 275 (98.9) | 271 (98.5) |
| Other | 2 (0.4) | 7 (1.3) | 3 (0.5) | 3 (1.1) | 4 (1.5) |
| History of influenza vaccination, n (%) | |||||
| 2013–2014 | 187 (33.8) | 196 (35.3) | 195 (34.9) | 102 (36.7) | 89 (32.4) |
| 2012–2013 | 177 (32.0) | 199 (35.9) | 199 (35.7) | 105 (37.8) | 97 (35.3) |
| 2011–2012 | 179 (32.4) | 209 (37.7) | 197 (35.3) | 104 (37.4) | 94 (34.2) |
| History of influenza diagnosis, n (%) | |||||
| 2013–2014 | 3 (0.5) | 3 (0.5) | 7 (1.3) | 3 (1.1) | 3 (1.1) |
| 2012–2013 | 7 (1.3) | 5 (0.9) | 8 (1.4) | 4 (1.4) | 3 (1.1) |
| 2011–2012 | 7 (1.3) | 6 (1.1) | 3 (0.5) | 4 (1.4) | 4 (1.5) |
Values are for all participants vaccinated. Abbreviations: IIV3-1, the trivalent inactivated influenza vaccine containing the B Victoria lineage strain; IIV3-2, the 2014–2015 licensed IIV3 containing the B Yamagata lineage strain; IIV4, the 2014–2015 formulation of the quadrivalent inactivated influenza vaccine.