Table 2. Characteristics of samples from influenza-like illness patients eligible for vaccine effectiveness analysis, Israel, influenza season 2015/16 (n = 1,658).
| Characteristics | Controls (n = 873) | Influenza types and subtypes of cases (n = 785) | Total (n = 1,658) | p valued | ||||
|---|---|---|---|---|---|---|---|---|
| Total A (n = 348)a | A(H1N1)pdm09 (n = 332) | A(H3N2) (n = 5) | A(H1N1)pdm09 + B (n = 11) | B (n = 448)a | ||||
| n (%)b | n (%)b | n (%)b | n (%)b | n (%)b | n (%)b | n (%)c | ||
| Age groups | ||||||||
| 6 months–17 years | 450 (55.2) | 129 (15.8) | 123 (15.1) | 0 (0) | 6 (0.7) | 242 (29.7) | 815 (49.2) | 0.83 |
| 18–44 years | 234 (45.0) | 142 (27.3) | 138 (26.5) | 1 (0.2) | 3 (0.6) | 147 (28.3) | 520 (31.4) | |
| 45–64 years | 131 (58.5) | 60 (26.8) | 56 (25.0) | 3 (1.3) | 1 (0.4) | 34 (15.2) | 224 (13.5) | |
| ≥ 65 years | 58 (58.6) | 17 (17.2) | 15 (15.1) | 1 (1.0) | 1 (1.0) | 25 (25.2) | 99 (6.0) | |
| Sex | ||||||||
| Male | 434 (52.8) | 178 (21.6) | 169 (20.6) | 3 (0.4) | 6 (0.7) | 216 (26.3) | 822 (49.6) | 0.91 |
| Female | 439 (52.5) | 170 (20.3) | 163 (19.5) | 2 (0.2) | 5 (0.6) | 232 (27.8) | 836 (50.4) | |
| Chronic medical conditions | ||||||||
| Yes | 172 (60.6) | 49 (17.2) | 45 (15.8) | 2 (0.7) | 2 (0.7) | 65 (22.9) | 284 (17.1) | < 0.01 |
| No | 696 (50.9) | 298 (21.8) | 286 (20.9) | 3 (0.2) | 9 (0.7) | 382 (28.0) | 1367 (82.4) | |
| Missing | 5 (71.4) | 1 (14.3) | 1 (14.3) | 0 (0) | 0 (0) | 1 (14.3) | 7 (0.4) | |
| Interval between symptom onset and swab | ||||||||
| 0–1 days | 386 (57.6) | 132 (19.7) | 124 (18.5) | 0 (0) | 8 (1.2) | 160 (23.9) | 670 (40.4) | < 0.01 |
| 2–4 days | 421 (48.9) | 188 (21.9) | 182 (21.2) | 3 (0.3) | 3 (0.3) | 254 (29.5) | 860 (51.9) | |
| 5–7 days | 66 (51.6) | 28 (21.9) | 26 (20.3) | 2 (1.6) | 0 (0) | 34 (26.6) | 128 (7.7) | |
| Vaccination statuse | ||||||||
| Unvaccinated | 742 (52.4) | 308 (21.7) | 294 (20.8) | 3 (0.2) | 11 (0.8) | 377 (26.6) | 1416 (85.4) | 0.62 |
| Vaccinated (TIV) | 131 (54.1) | 40 (16.5) | 38 (15.7) | 2 (0.8) | 0 (0) | 71 (29.3) | 242 (14.6) | |
TIV: trivalent inactivated vaccine.
a The 11 samples positive for influenza A(H1N1)pdm09 and influenza B are included in both the count of 'Total A' column and the 'B' column.
b Percentage based on total of each row.
c Percentage based on the total of 1,658.
d Analysis performed for influenza positive (cases) vs negative (controls).
e Individuals receiving quadrivalent inactivated influenza vaccine (QIV) (n=12) were excluded from the table and analysis.