Table 1.
Characteristics of Participating Household Members During the 2013–2014 Influenza Season, by Documented Influenza Vaccine Receipt and 2009 Pandemic Influenza A(H1N1) Virus (Influenza A[H1N1]pdm09) Infection Status: Household Influenza Vaccine Effectiveness Study, Ann Arbor, Michigan
| Participant Characteristics | All Subjects, No. (%) (n = 1049) | Documented Influenza Vaccination, No. (%)a | Influenza A(H1N1)pdm09 Infection, No. (%)b |
|---|---|---|---|
| Age, y | |||
| <9 | 314 (29.9) | 225 (71.7)c,d | 22 (7.0)e |
| 9–17 | 304 (29.0) | 191 (62.8) | 5 (1.6) |
| 18–49 | 380 (36.2) | 215 (56.6) | 20 (5.3) |
| ≥50 | 51 (4.9) | 30 (58.8) | 0 (0.0) |
| Race | |||
| White | 823 (78.5) | 534 (64.9)d | 34 (4.1)e |
| Asian | 83 (7.9) | 57 (68.7) | 6 (7.2) |
| Black | 61 (5.8) | 35 (57.4) | 0 (0.0) |
| Other/unknown | 82 (7.8) | 35 (42.7) | 7 (8.5) |
| Sex | |||
| Female | 529 (50.4) | 339 (64.1) | 24 (4.5) |
| Male | 520 (49.6) | 322 (61.9) | 23 (4.4) |
| High-risk health condition | |||
| Any | 126 (12.0) | 88 (69.8) | 10 (7.9)e |
| None | 923 (88.0) | 573 (62.1) | 37 (4.0) |
| Documented influenza vaccinationa | |||
| Yes | 661 (63.0) | … | 16 (2.4)d |
| No | 388 (37.0) | … | 31 (8.0) |
| Overall | 1049 (100) | 661 (63.0) | 47f (4.5) |
a Vaccination was defined as at least 1 dose influenza vaccine received during the 2013–2014 vaccination period, as documented in the medical record or state immunization registry; subjects with laboratory-confirmed influenza A(H1N1)pdm09 virus infection were considered vaccinated if vaccine was administered ≥14 days prior to illness onset. The denominator for percentages is all subjects (vaccinated or unvaccinated) with the specified characteristic.
b The denominator for percentages is all subjects (with or without influenza A[H1N1]pdm09 infection) with the specified characteristic.
c A total of 217 of 225 vaccinated children (96.4%) <9 years of age were considered fully vaccinated, as defined by Advisory Committee on Immunization Practices recommendations.
d P<.001, by the Pearson χ2 or Fisher exact tests, comparing vaccinated and unvaccinated subjects or subjects with and those without laboratory-confirmed influenza.
e P<.05, by the Pearson χ2 or Fisher exact tests, comparing vaccinated and unvaccinated subjects or subjects with and those without laboratory-confirmed influenza.
f This value denotes the 47 cases of influenza A(H1N1)pdm09 infection identified in 47 individuals.