Table 2. Unadjusted and Adjusted Risk Ratios for Influenza Vaccination for Subgroups vs a Reference Subgroup and for Each Study Group vs the No Reminder Control Group.
| Subgroup | Risk ratio (95% CI)a | |
|---|---|---|
| Unadjusted | Adjusted | |
| Study group | ||
| 0 Reminders | 1 [Reference] | 1 [Reference] |
| 1 Reminder | 1.01 (1.00-1.03) | 1.02 (1.00-1.03) |
| 2 Reminders | 1.02 (1.00-1.04) | 1.02 (1.00-1.04) |
| 3 Reminders | 1.02 (1.00-1.04) | 1.02 (1.00-1.04) |
| Age group, y | ||
| 0.5-17 | 1 [Reference] | 1 [Reference] |
| 18-64 | 0.70 (0.66-0.75) | 0.78 (0.74-0.82) |
| ≥65 | 1.13 (1.04-1.23) | 0.97 (0.92-1.02) |
| Sex | ||
| Male | 1 [Reference] | 1 [Reference] |
| Female | 0.98 (0.96-1.00) | 1.00 (0.99-1.02)a |
| Insuranceb | ||
| Private | 1 [Reference] | 1 [Reference] |
| Public | 1.45 (1.36-1.54) | 1.04 (1.02-1.05) |
| Other or unknown | 0.95 (0.89-1.02) | 0.95 (0.90-1.00) |
| Race | ||
| White | 1 [Reference] | 1 [Reference] |
| Black | 0.78 (0.75-0.82) | 0.89 (0.86-0.92) |
| Asian | 1.07 (1.04-1.10) | 1.04 (1.02-1.06) |
| Other or unknown | 0.81 (0.79-0.84) | 0.91 (0.90-0.93) |
| Ethnicity | ||
| Non-Hispanic or unknown | 1 [Reference] | 1 [Reference] |
| Hispanic | 0.96 (0.93-0.99) | 1.01 (0.99-1.04) |
| Received influenza vaccination in prior 2 y | ||
| No | 1 [Reference] | 1 [Reference] |
| Yes | 3.85 (3.65-4.07) | 3.70 (3.51-3.91) |
a
1.00 is a rounded figure, but all the adjusted lower bounds of the 95% CIs were strictly greater than 1.
b
Most publicly insured patients in this health care system are older adults on Medicare or children on Medicaid, accounting for higher influenza vaccination rates among these patients.