Table 1. Influenza incidence rates according to subpopulation, diagnostic methods and vaccination status.
| Subpopulation | Diagnostic methods | Vaccination status | Number of seasons | Number of Subjects | I2 (P value) | Incidence rate [95% confidence interval](n/100 population/season) |
| Families1 | All infections | Unvaccinated | 1 | 62 | NA | 24.19 [15.05, 38.89] |
| Unknown | 9 | 1,951 | 81% (<0.001) | 13.56 [10.25, 17.94] | ||
| Symptomatic infections (serology) | Unknown | 1 | 96 | NA | 20.83 [13.75, 31.56] | |
| Symptomatic infections (culture) | Unknown | 9 | 1,533 | 79% (<0.001) | 4.96 [2.82, 8.71] | |
| Working adults | All infections | Unvaccinated | 4 | 4,373 | 93% (<0.001) | 5.44 [3.01, 9.84] |
| Vaccinated | 2 | 3,717 | 16% (0.28) | 1.20 [0.86, 1.68] | ||
| Unknown | 6 | 2,479 | 91% (<0.001) | 9.13 [5.95, 14.01] | ||
| Symptomatic infections (serology) | Unvaccinated | 4 | 1,234 | 66% (0.03) | 5.12 [3.08, 8.52] | |
| Vaccinated | 3 | 2,619 | 68% (0.04) | 3.04 [1.79, 5.15] | ||
| Unknown | 2 | 1,446 | 63% (0.10) | 1.22 [0.48, 3.05] | ||
| Symptomatic infections (culture) | Unvaccinated | 8 | 9,393 | 90% (<0.001) | 2.91 [1.78, 4.75] | |
| Vaccinated | 8 | 14,017 | 89% (<0.001) | 1.35 [0.76, 2.41] | ||
| Symptomatic infections (PCR) | Unvaccinated | 1 | 325 | NA | 10.77 [7.76, 14.94] | |
| Vaccinated | 1 | 1,627 | NA | 5.16 [4.17, 6.40] | ||
| HCWs | All infections | Unvaccinated | 10 | 2,273 | 66% (0.002) | 18.69 [15.80, 22.11] |
| Vaccinated | 8 | 3.026 | 73% (<0.001) | 6.49 [4.63, 9.09] | ||
| Unknown | 1 | 250 | NA | 11.20 [7.76, 16.17] | ||
| Symptomatic infections (serology) | Unvaccinated | 7 | 1,857 | 81% (<0.001) | 7.54 [4.86, 11.70] | |
| Vaccinated | 7 | 3,092 | 76% (<0.001) | 4.81 [3.23, 7.16] | ||
| Unknown | 1 | 250 | NA | 8.00 [5.12, 12.49] | ||
| Symptomatic infections (culture) | Unvaccinated | 2 | 1,505 | 99% (<0.001) | 6.24 [0.83, 46.88] | |
| Vaccinated | 1 | 698 | NA | 0.43 [0.11, 1.61] | ||
| Symptomatic infections (PCR) | Unknown | 1 | 422 | NA | 2.37 [1.22, 4.61] |
Abbreviations: CI, confidence interval; NA, not applicable; HCWs, healthcare workers.
1
Working-age adults living in households with children.