Table 3. Primary and subgroup analyses by intention to treat.
| Intervention n/N (%) | Control n/N (%) | OR (95% CI) | Interaction p value | |
|---|---|---|---|---|
| Clinical respiratory infection | 354/3,199 (11.1) | 322/3,139 (10.3) | 1.1 (0.9–1.4) | |
| Influenza vaccinated | 160/1,677 (9.5) | 181/1,631 (11.1) | 0.8 (0.7–1.1) | < 0.01 |
| Not vaccinated or vaccination status reported as unknown | 176/1,361 (12.9) | 131/1,381 (9.5) | 1.4 (1.0–2.0) | |
| At increased risk | 86/621 (13.8) | 69/615 (11.2) | 1.3 (0.9–1.8) | 0.28 |
| Not at increased risk | 254/2,439 (10.4) | 239/2,399 (10) | 1.1 (0.8–1.4) | |
| Smoking as the single risk factor | 40/350 (11.4) | 30/311 (9.6) | 1.2 (0.7–2) | 0.86 |
| Non-smoking | 303/2,721 (11.1) | 279/2,725 (10.2) | 1.1 (0.8–1.4) | |
| Male | 148/1,576 (9.4) | 120/1,354 (8.9) | 1.1 (0.8–1.5) | 0.73 |
| Female | 206/1,623 (12.7) | 202/1,785 (11.3) | 1.2 (0.9–1.6) | |
| Gulf | 332/3,043 (10.9) | 287/2,954 (9.7) | 1.2 (0.9–1.5) | 0.13 |
| Australia | 22/156 (14.1) | 35/185 (18.9) | 0.7 (0.4–1.3) | |
| Laboratory-confirmed viral respiratory infection | 96/218 (44) | 60/161 (37.3) | 1.4 (0.9–2.1) | - |
| Influenza vaccinated | 44/106 (41.5) | 37/102 (36.3) | 1.3 (0.7–2.2) | 0.85 |
| Not vaccinated or vaccination status reported as unknown | 54/95 (56.8) | 21/53 (39.6) | 1.3 (0.7–2.2) | |
| At increased risk | 20/42 (47.6) | 12/31 (38.7) | 3 (1.9–4.9) | 0.71 |
| Not at increased risk | 71/164 (43.3) | 45/114 (39.5) | 1.2 (0.7–2.1) | |
| Smokers | 11/28 (39.3) | 5/9 (55.6) | 0.5 (0.1–2.8) | 0.33 |
| Not smokers | 80/179 (44.7) | 53/138 (38.4) | 1.3 (0.8–2) | |
| Male | 45/101 (44.6) | 28/50 (56) | 0.7 (0.3–1.4) | 0.02 |
| Female | 51/117 (43.6) | 32/111 (28.8) | 1.9 (1.2–3) | |
| Gulf countries | 15/35 (42.9) | 17/48 (35.4) | 1.4 (0.6–3.4) | 0.96 |
| Australia | 81/183 (44.3) | 43/113/ (38.1) | 1.3 (0.8–2.2) |