BACKGROUND:
Many nursing home residents are unimmunized or have unknown immunization status for influenza vaccination.

OBJECTIVE:
To identify resident and facility characteristics associated with not receiving influenza immunization and with unknown immunization status.

METHOD:
Multinomial logistic regression using a nationally representative sample of 7,350 nursing home residents >65 years old in 1,423 facilities in 1999. The outcome is record-based staff report of whether residents received influenza vaccination during the past 12 months (yes/no/unknown).

RESULT:
Fifteen percent were not immunized and 19 percent had unknown immunization status. In multivariate analysis (95% CIs), lack of and unknown immunization were both associated with shorter length of stay (<6 months), no or unknown pneumococcal immunization, and facility failures to screen for immunization at admission and record it in the medical record. Living in a Medicaid-certified-only facility lowered the odds of no vaccination and of unknown status. Unvaccinated residents were younger than those vaccinated. Residents with unknown immunization were more likely to have Medicare or private insurance, eat independently and live in non-certified facilities than those vaccinated. High-risk groups and staff immunizations had no effect. Separate analyses showed that residents with unknown immunization are statistically significantly different from both those vaccinated and those not.

CONCLUSION:
About 34 percent of residents did not receive immunization or had unknown status. Resident and facility characteristics influence these rates, suggesting targeted education of residents and facility screening and recording of immunization. Residents with unknown immunization are different on important characteristics from both the vaccinated and the unvaccinated and should be evaluated separately.

LEARNING OBJECTIVES:
Understanding that both resident and facility characteristics are associated with not receiving vaccine or unknown status; that high risk groups and staff immunizations do not influence immunization rates; and that residents with unknown vaccination status should not be lumped with other groups.