Hunter S, Garbinsky D, La EM, Poston S, Hogea C. Impact of state of residence on adult vaccination uptake: a multilevel modeling approach. Presented at the IDWeek 2020 Virtual Conference; October 21, 2020.

BACKGROUND: Previous studies on adult vaccination coverage found inter-state variability that persists after adjusting for individual demographic factors. Assessing the impact of state-level factors may help improve uptake strategies. This study aimed to:

•  Update previous estimates of state-level, model-adjusted coverage rates for influenza; pneumococcal; tetanus, diphtheria, and acellular pertussis (Tdap); and herpes zoster (HZ) vaccines (individually and in compliance with all age-appropriate recommended vaccinations)
•  Evaluate effects of individual and state-level factors on adult vaccination coverage using a multilevel modeling framework.

METHODS: Behavioral Risk Factor Surveillance System (BRFSS) survey data (2015-2017) were retrospectively analyzed. Multivariable logistic regression models estimated state vaccination coverage and compliance using predicted marginal proportions. BRFSS data were then combined with external state-level data to estimate multilevel models evaluating effects of state-level factors on coverage. Weighted odds ratios and measures of cluster variation were estimated.

RESULTS: Adult vaccination coverage and compliance varied by state, even after adjusting for individual characteristics, with coverage ranging as follows:

•  Influenza (2017): 35.1-48.1%
•  Pneumococcal (2017): 68.2-80.8%
•  Tdap (2016): 21.9-46.5%
•  HZ (2017): 30.5-50.9%

Few state-level variables were retained in final multilevel models, and measures of cluster variation suggested substantial residual variation unexplained by individual and state-level variables. Key state-level variables positively associated with vaccination included health insurance coverage rates (influenza/HZ), pharmacists’ vaccination authority (HZ), presence of childhood vaccination exemptions (pneumococcal/Tdap), and adult immunization information system participation (Tdap/HZ).

CONCLUSION: Adult vaccination coverage and compliance continue to show substantial variation by state even after adjusting for individual and state-level characteristics associated with vaccination. Further research is needed to assess additional state or local factors impacting vaccination disparities.

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