Table 4.
Subject characteristics and risk of admission with influenza
| All admissions | Influenza-positive | Crude OR | Heterogeneity by strain (I2)a | aORb | ||||
|---|---|---|---|---|---|---|---|---|
| N = 9164 | N = 2177 | |||||||
| Characteristic | n | n | % | Value | 95 % CI | Value | 95 % CI | |
| Age | ||||||||
| 0–1 y | 1515 | 144 | 9.5 | 1.00 | - | 32.5 % | 1.00 | - |
| 2–4 y | 2206 | 429 | 19.4 | 2.30 | 1.88-2.81 | 0.0 % | 2.14 | 1.74-2.64 |
| 5–17 y | 827 | 280 | 33.9 | 4.87 | 3.90-6.10 | 73.3 % | 4.34 | 3.42-5.51 |
| 18–49 y | 1461 | 423 | 29.0 | 3.88 | 3.16-4.77 | 59.2 % | 3.11 | 2.49-3.90 |
| 50–64 y | 748 | 191 | 25.5 | 3.26 | 2.57-4.14 | 72.5 % | 4.08 | 3.11-5.36 |
| 65–74 y | 819 | 211 | 25.8 | 3.30 | 2.62-4.17 | 67.8 % | 4.99 | 3.76-6.64 |
| 75–84 y | 1227 | 294 | 24.0 | 3.00 | 2.42-3.72 | 62.4 % | 4.51 | 3.43-5.92 |
| ≥85 | 811 | 205 | 25.3 | 3.22 | 2.55-4.07 | 71.2 % | 4.79 | 3.59-6.40 |
| Sexc | ||||||||
| Male | 5417 | 1141 | 21.1 | 1.00 | - | 0.0 % | 1.00 | - |
| Female | 4197 | 1036 | 24.7 | 1.24 | 1.13-1.37 | 0.0 % | 1.21 | 1.09-1.34 |
| Female non-pregnant | 3899 | 876 | 22.5 | 1.11 | 1.00-1.22 | 0.0 % | 1.10 | 0.99-1.23 |
| Other risk factors (excludes pregnant women) | ||||||||
| Comorbidityd | 3709 | 856 | 23.1 | 1.15 | 1.04-1.27 | 62.8 % | 1.48 | 1.30-1.69 |
| Cardiovascular disease | 1996 | 468 | 23.4 | 1.17 | 1.04-1.33 | 22.2 % | 1.47 | 1.25-1.72 |
| Chronic obstructive pulmonary disease | 1458 | 306 | 21.0 | 1.02 | 0.88-1.17 | 57.6 % | 1.39 | 1.15-1.68 |
| Asthma | 440 | 96 | 21.8 | 1.07 | 0.84-1.35 | 0.0 % | 1.37 | 1.04-1.80 |
| Immunosuppression | 106 | 14 | 13.2 | 0.58 | 0.33-1.03 | 0.0 % | 0.76 | 0.40-1.46 |
| Diabetes | 1048 | 234 | 22.3 | 1.10 | 0.94-1.29 | 0.0 % | 1.36 | 1.10-1.70 |
| Renal disease | 588 | 129 | 21.9 | 1.08 | 0.88-1.32 | 48.2 % | 1.23 | 0.95-1.59 |
| Neuromuscular | 167 | 52 | 31.1 | 0.93 | 0.68-1.26 | 38.9 % | 1.13 | 0.80-1.58 |
| Neoplasm (active) | 301 | 63 | 20.9 | 1.01 | 0.76-1.35 | 55.6 % | 1.29 | 0.92-1.81 |
| Liver disease | 200 | 33 | 16.5 | 0.76 | 0.52-1.11 | 50.8 % | 0.79 | 0.52-1.21 |
| Autoimmune disease | 161 | 39 | 24.2 | 1.22 | 0.85-1.77 | 0.0 % | 1.44 | 0.95-2.18 |
| Obesee | 1620 | 337 | 20.8 | 1.0 | 0.9-1.2 | 0.0 % | 0.87 | 0.73-1.03 |
| Pregnancyf | 298 | 160 | 53.7 | 3.45 | 2.23-5.34 | 0.0 % | 2.08 | 1.43-3.03 |
| Associated comorbidity | 38 | 26 | 68.4 | 7.07 | 3.09-16.18 | 0.0 % | 4.29 | 2.65-6.94 |
| No comorbidity | 260 | 126 | 48.5 | 3.05 | 2.08-4.47 | 0.0 % | 1.80 | 1.22-2.66 |
aStrains considered: A(H3N2), A(H1N1)pdm09 and B/Yamagata
bMinimal sufficient adjustment sets for estimating the exposure or risk factor effect on the risk of admission with influenza vs. all included admissions without underlying conditions or pregnant
cFemale or female non-pregnant vs. male. aORs were adjusted for age, occupational social class group, underlying comorbidity, obesity, influenza vaccination, time to swab, calendar time, and site as a clustering factor
dOne or more underlying conditions or individual comorbidities vs. no comorbidity. aORs were adjusted for sex, occupational social class group, obesity, influenza vaccination, time to swab, calendar time, and site as a clustering factor
eaOR adjusted for sex, age, occupational social class group, influenza vaccination, time to swab, calendar time, and site as a clustering factor
fWomen 15-45 years of age included in Moscow, St. Petersburg, Czech Republic, Turkey and Valencia. aOR adjusted for smoking habits, time to swab, calendar time, comorbidity, and site as a clustering factor. For results stratified by comorbidity, aORs were adjusted by the same covariates and were estimated taking into account the interaction between pregnancy and comorbidity