Table 2. Characteristics of influenza A(H3N2) cases and test negative controls in Spain, seasons 2011–2012, 2013–2014 and 2014–2015.
| Influenza season | 2011–2012 | 2013–2014 | 2014–2015 | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Controls | Cases | Controls | Cases | Controls | Cases | ||||
| N (%) | N (%) | p | N (%) | N (%) | p | N (%) | N (%) | p | |
| Total | 430 (100) | 674 (100) | 440 (100) | 322 (100) | 358 (100) | 362 (100) | |||
| Age groups (years) | .016 | .876 | .003 | ||||||
| 9–14 | 53 (12) | 83 (12) | 50 (11) | 32 (10) | 56 (16) | 84 (23) | |||
| 15–44 | 223 (52) | 301 (45) | 220 (50) | 159 (49) | 160 (45) | 158 (44) | |||
| 45–64 | 116 (27) | 191 (28) | 120 (27) | 90 (28) | 110 (31) | 76 (21) | |||
| ≥65 | 38 (9) | 99 (15) | 50 (11) | 41 (13) | 32 (9) | 44 (12) | |||
| Sex | .788 | .542 | .374 | ||||||
| Male | 209 (49) | 322 (48) | 217 (49) | 166 (52) | 178 (50) | 168 (46) | |||
| Female | 221 (51) | 352 (52) | 223 (51) | 156 (48) | 180 (50) | 194 (54) | |||
| Target groups | .023 | .817 | .866 | ||||||
| No | 320 (75) | 461 (68) | 300 (68) | 217 (67) | 267 (75) | 268 (74) | |||
| Yes | 108 (25) | 213 (32) | 140 (32) | 105 (33) | 91 (25) | 94 (26) | |||
| Major chronic conditions | .836 | .421 | .981 | ||||||
| No | 365 (85) | 569 (84) | 343 (78) | 243 (75) | 291 (81) | 294 (81) | |||
| Yes | 65 (15) | 105 (16) | 97 (22) | 79 (25) | 67 (19) | 68 (19) | |||
| Previous influenza vaccine | .805 | .706 | .208 | ||||||
| No | 374 (87) | 581 (86) | 380 (86) | 275 (85) | 324 (91) | 317 (88) | |||
| Yes | 56 (13) | 91 (14) | 60 (14) | 47 (15) | 34 (9) | 45 (12) | |||
| Current influenza vaccine | .517 | .424 | .531 | ||||||
| No | 371 (86) | 572 (85) | 382 (87) | 273 (85) | 317 (89) | 315 (87) | |||
| Yes | 59 (14) | 102 (15) | 58 (13) | 49 (159 | 41 (11) | 47 (13) | |||
| Onset-swabbing ≤ 4days | .062 | .697 | .197 | ||||||
| No | 18 (4) | 15 (2) | 10 (2) | 6 (2) | 7 (2) | 3 (1) | |||
| Yes | 412 (96) | 659 (98) | 430 (98) | 316 (98) | 351 (98) | 359 (99) | |||