Table 2.
Association between risk exposures, preventive measures and the diagnosis of laboratory‐confirmed influenza in the bivariate and multivariate analyses
| Cases* (n = 481) n (%) | Controls* (n = 481) n (%) | Crude OR (95% CI)** | P value | Adjusted OR (95% CI)*** | P value | |
|---|---|---|---|---|---|---|
| No. cohabitants | ||||||
| 1–2 | 136 (28·9) | 204 (43·5) | Reference | Reference | ||
| 3 | 133 (28·2) | 119 (25·4) | 1·95 (1·35–2·82) | <0·001 | 1·80 (1·12–2·89) | 0·015 |
| 4 | 154 (32·7) | 114 (24·3) | 2·27 (1·59–3·22) | <0·001 | 2·03 (1·28–3·20) | 0·002 |
| 5 or more | 48 (10·2) | 32 (6·8) | 3·02 (1·74–5·24) | <0·001 | 2·66 (1·31–5·41) | 0·007 |
| Health care worker | ||||||
| No | 392 (81·5) | 451 (93·8) | Reference | Reference | ||
| Yes | 89 (18·5) | 30 (6·2) | 3·81 (2·36–6·16) | <0·001 | 2·94 (1·53–5·66) | 0·001 |
| Use of transportation | ||||||
| Metro, bus, tram or local train† | ||||||
| No | 257 (54·0) | 201 (42·0) | Reference | Reference | ||
| Yes | 219 (46·0) | 278 (58·0) | 0·55 (0·41–0·74) | <0·001 | 0·45 (0·30–0·68) | <0·001 |
| Train or plane† | ||||||
| No | 388 (82·4) | 391 (82·0) | Reference | Reference | ||
| Yes | 83 (17·6) | 86 (18·0) | 0·97 (0·58–1·37) | 0·859 | 0·80 (0·50–1·28) | 0·346 |
| Taxi** | ||||||
| No | 403 (85·2) | 400 (83·5) | Reference | Reference | ||
| Yes | 70 (14·8) | 79 (16·5) | 0·86 (0·59–1·26) | 0·446 | 1·19 (0·70–2·04) | 0·522 |
| Preventive measures | ||||||
| Influenza A(H1N1)2009 vaccination | ||||||
| No | 477 (99·2) | 463 (96·3) | Reference | Reference | ||
| Yes | 4 (0·8) | 18 (3·7) | 0·24 (0·08–0·70) | 0·009 | 0·13 (0·04–0·48) | 0·002 |
| Hand washing† | ||||||
| 4 or less times/day | 122 (25·6) | 123 (25·6) | Reference | Reference | ||
| 5–10 times/day | 161 (33·8) | 185 (38·5) | 0·91 (0·64–1·28) | 0·574 | 0·87 (0·54–1·39) | 0·555 |
| More than 10 times/day | 193 (40·5) | 173 (36·0) | 1·13 (0·79–1·60) | 0·514 | 0·98 (0·59–1·64) | 0·936 |
| Hand washing after touching contaminated surfaces† | ||||||
| Never–occasional | 197 (41·4) | 174 (36·4) | Reference | Reference | ||
| Frequently–always | 279 (58·6) | 304 (63·6) | 0·72 (0·52–0·99) | 0·044 | 0·70 (0·44–1·11) | 0·132 |
| Alcohol‐based hand sanitizers† | ||||||
| Never–occasional | 350 (73·4) | 398 (82·9) | Reference | Reference | ||
| Frequently–always | 127 (26·6) | 82 (17·1) | 1·80 (1·30–2·50) | <0·001 | 1·36 (0·85–2·19) | 0·197 |
*Some variables had missing values.
**Odds ratio and confidence intervals obtained by crude conditional logistic regression.
***Odds ratio and confidence intervals obtained by conditional logistic regression adjusted for sex, age, educational level, pregnancy, smoking, major risk conditions, type of interview and the variables shown in the table. After excluding missing values, 441 case–control pairs were included in the multivariate analysis.
†Refers to 7 days prior to symptom onset in cases or medical consultation in controls.