Table 1.
Characteristics of All Participants and Participants With ≥2 Febrile Respiratory Illness (FRI) Episodes
| Characteristic | All Participants, No. | Participants With ≥2 FRI Episodes, No. (%) | OR for Having ≥2 FRI Episodes (95% CI) | P a |
|---|---|---|---|---|
| Study year(s) | ||||
| 2009/2010 | 1510 | 127 (8.4) | Reference | <.001 |
| 2011 | 1315 | 140 (10.6) | 1.30 (1.01–1.67) | |
| 2012 | 1160 | 65 (5.6) | .65 (.47–.88) | |
| 2013 | 841 | 54 (6.4) | .75 (.54–1.04) | |
| 2014 | 851 | 37 (4.3) | .49 (.34–.72) | |
| Type of BMT intake | ||||
| 19-week | 1357 | 164 (12.1) | Reference | <.001 |
| 17-week | 2677 | 228 (8.5) | .68 (.55–.84) | |
| 9-week | 1276 | 24 (1.9) | .14 (.09–.22) | |
| Otherb | 367 | 7 (1.9) | .14 (.07–.30) | |
| Sex | ||||
| Male | 5672 | 423 (7.5) | Reference | 1.000 |
| Female | 5 | 0 (0.0) | … | |
| Ethnicity | ||||
| Chinese | 4362 | 304 (7.0) | Reference | .036 |
| Malay | 780 | 73 (9.4) | 1.38 (1.05–1.80) | |
| Indian | 322 | 32 (9.9) | 1.47 (1.00–2.16) | |
| Other | 213 | 14 (6.6) | .94 (.54–1.63) | |
| Smoking history | ||||
| Never | 4277 | 285 (6.7) | Reference | <.001 |
| Former | 147 | 18 (12.2) | 1.95 (1.18–3.25) | |
| Current | 1253 | 120 (9.6) | 1.48 (1.19–1.85) | |
| History of asthma | ||||
| No | 4340 | 326 (7.5) | Reference | .812 |
| Yes | 1337 | 97 (7.3) | .08 (.07–.09) | |
| Influenza vaccinationc | ||||
| No recent influenza vaccination | 930 | 97 (10.4) | Reference | .003 |
| MIV for A(H1N1)pdm09 only | 981 | 73 (7.4) | .69 (.50–.95) | |
| TIV only | 3719 | 250 (6.7) | .62 (.48–.79) | |
| Both MIV and TIV | 47 | 3 (6.4) | .59 (.18–1.92) |
Abbreviations: A(H1N1)pdm09, 2009 pandemic influenza A(H1N1) virus; BMT, basic military training; CI, confidence interval; MIV, monovalent influenza vaccine; OR, odds ratio; TIV, trivalent influenza vaccine.
aBy the Fisher exact test, comparing participants with 1 FRI episode to those with >1 FRI episode.
bA mix of shorter BMT intake types.
cUp to 1 year before first FRI episode (those reporting vaccination >1 year ago are considered unvaccinated). Participants can receive either or both vaccine formulations.