Article Title

Geographic Disparities in Influenza Vaccination Among Patients at Kaiser Permanente Mid-Atlantic States, 2014–2015

Publication Date



influenza, disparities


Background/Aims: Yearly influenza epidemics can result in increased morbidity and mortality, absenteeism and productivity losses, and can overwhelm clinics and hospitals during peak illness periods. While safe and effective vaccines are available, disparities in influenza vaccinations rates are reported. The goal of this study is to examine geographic patterns of influenza vaccinations at Kaiser Permanente Mid-Atlantic States (KPMAS) (and assess the relative contribution of select covariates –– data not presented here).

Methods: We included members ≥ 18 years old as of May 1, 2014, with continuous enrollment through May 31, 2015. Influenza vaccination was defined by diagnosis, procedure or medication codes, or documentation in the immunization table. Characteristics of those who did and did not receive the vaccine were reported. Vaccination rates were examined by county for Maryland (MD), District of Columbia (DC) and Virginia (VA). We will use the Blinder-Oaxaca decomposition method to determine what proportion of the geographic disparity could be reduced by equalizing select characteristics (data to be presented later).

Results: We identified 348,666 adult KPMAS members, of whom 141,238 (40.5%) received the influenza vaccine. Vaccinated, compared to nonvaccinated, members were younger (mean age 55 [SD: 16.7] vs. 43 [SD: 16.2]), more likely to be white (56,123 [39.7%] vs. 49,435 [23.8%]) and less likely to be African-American (47,028 [33.3%] vs. 80,819 [39.0%]). Education, mean distance to a medical center, body mass index and current smoking status were similar across the two groups. Vaccinated members were more likely to have had a primary care visit in the study year (126,677 [89.7%]) than nonvaccinated members (134,011 [64.6%]). Geographically, the lowest rates of influenza vaccinations (< 30%) were clustered in six adjacent counties located in DC and southern MD. Northern VA counties had the highest rates of vaccination. By race, vaccination rates were lower for African-Americans compared to whites in every county; however, a similar geographic pattern of low vaccination rates was observed in both races.

Conclusion: Among KPMAS members, a cluster of counties in DC and southern MD show the lowest rates of vaccinations. Examination of possible reasons for this disparity are needed. In subsequent analyses we will determine how specific characteristics contribute to the geographic disparity.