Table 5. Sensitivity analysis of trivalent inactivated influenza vaccine effectiveness in preventing medically attended laboratory confirmed influenza, Israel, influenza seasons 2014/15 and 2015/16 (n = 1,005 and 1,658, respectively).
| Influenza Season | Influenza type/subtype | Time of sample collection | Cases | Controls | Crude VE | Adjusted VEa | ||
|---|---|---|---|---|---|---|---|---|
| Vaccinated | Unvaccinated | Vaccinated | Unvaccinated | % (95% CI) | % (95% CI) | |||
| 2014/15 | A + B | < 2 days after disease onset | 34 | 115 | 59 | 306 | −53.3 (−146.2 to 4.5) | −41.8 (−144.5 to 17.7) |
| 2–7 days after disease onset | 25 | 133 | 62 | 271 | 17.8 (−36.6 to 50.6) | 20.9 (−39.8 to 55.2) | ||
| A(H3N2) | < 2 days after disease onset | 31 | 95 | 59 | 306 | −69.3 (−176.9 to −3.5) | −61.9 (−183.0 to 7.4) | |
| 2–7 days after disease onset | 22 | 109 | 62 | 271 | 11.8 (−50.6 to 48.3) | 14.7 (−153.7 to 52.7) | ||
| 2015/16 | A + B | < 2 days after disease onset | 32 | 252 | 52 | 334 | 18.4 (−30.5 to 49.0) | 22.8 (−29.1 to 53.9) |
| 2–7 days after disease onset | 79 | 422 | 79 | 408 | 3.3 (−35.9 to 31.2) | 1.1 (−49.3 to 34.5) | ||
| A(H1N1)pdm09b | < 2 days after disease onset | 14 | 118 | 52 | 334 | 23.8 (−42.6 to 59.3) | −47.8 (−192.4 to 25.3) | |
| 2–7 days after disease onset | 24 | 187 | 79 | 408 | 33.7 (−8.1 to 59.3) | −41.0 (−147.4 to 19.6) | ||
| Bb | < 2 days after disease onset | 18 | 142 | 52 | 334 | 18.6 (−44.1 to 54.0) | 26.7 (−37.1 to 60.8) | |
| 2–7 days after disease onset | 53 | 235 | 79 | 408 | −16.5 (−70.9 to 20.6) | −18.5 (−88.8 to 25.6) | ||
a Adjusted for age group, sex and calendar week for 2014/15, and adjusted for age group, sex, calendar week and underlying condition for 2015/16.
b The 11 samples positive for influenza A(H1N1)pdm09 and influenza B in the 2015/16 season are included in the analysis of influenza A(H1N1)pdm09 and influenza B.