Table 3.
Vaccine Effectiveness (VE) Using Conditional Logistic Regressiona to Estimate Laboratory-Confirmed Influenza-Related Visits by Vaccination Status, Age Group, and Influenza Season
| Vaccination Status | aOR (95% CI) | VE (%) (95% CI) | aOR (95% CI) | VE (%) (95% CI) | aOR (95% CI) | VE (%) (95% CI) |
|---|---|---|---|---|---|---|
| 2003-2004 | ||||||
| Aged 6–59 mo (N = 971) | Aged 6–23 mo (N = 537) | Aged 24–59 mo (N = 434) | ||||
| Fully vaccinatedb | 0.56 (0.22-1.42) | 44 (-42-78) | 0.72 (0.23-2.30) | 28 (-130-77) | 0.34 (0.06-2.06) | 66 (-106-94) |
| Partially vaccinatedb | 0.57 (0.32-1.03) | 43 (-3-68) | 0.58 (0.27-1.22) | 42 (-22-73) | 0.67 (0.22-2.09) | 33 (-109-78) |
| Age (months)c | 1.01d (1.00-1.03) | 1.05 (1.00-1.11) | 0.98 (0.96-1.01) | |||
| Public/no insurancef | 1.05 (0.70-1.59) | 1.00 (0.55-1.83) | 1.02 (0.54-1.91) | |||
| Underlying medical condition | 0.84 (0.55-1.29) | 1.18 (0.62-2.25) | 0.62 (0.34-1.13) | |||
| 2004-2005 | ||||||
| Aged 6–59 mo (N =1,493) | Aged 6–23 mo (N = 860) | Aged 24–59 mo (N = 633) | ||||
| Fully vaccinatedb | 0.43d (0.26-0.72) | 57 (28-74) | 0.45e (0.23-0.87) | 55 (13-77) | 0.37e (0.16-0.84) | 63 (16-84) |
| Partially vaccinatedb | 0.89 (0.59-1.35) | 11 (-35-41) | 1.03 (0.62-1.70) | -3 (-70-38) | 0.62 (0.25-1.53) | 38 (-53-75) |
| Age (months)c | 1.00 (0.99-1.02) | 1.03 (0.99-1.08) | 1.00 (0.98-1.03) | |||
| Public/no insurancef | 1.43d (0.99-2.06) | 1.86e (1.07-3.22) | 1.23 (0.73-2.07) | |||
| Underlying medical condition | 1.03 (0.70-1.51) | 0.97 (0.55-1.72) | 1.10 (0.63-1.93) | |||
a
Controls were frequency matched to cases on site (Cincinnati, Nashville, or Rochester), visit setting (Inpatient/ED or Clinic), and date of enrollment (controls)/date of influenza symptom onset (cases).
b
Reference = unvaccinated.
c
Indicates unit increase for each additional month of age.
d
P<.01
e
P<.05; otherwise not significant.
f
Reference = private insurance.