This thesis aimed to elucidate the demographic characteristics associated with elevated or reduced rates of pneumococcal conjugate 13 (PCV13) vaccination. A retrospective cohort study was performed using the Truven Health MarketScan® Database. Three cohorts were created corresponding to populations for which the CDC recommends PCV13 vaccination. Cohort 1: children < 36 months of age. Cohort 2: adults 19-64 years of age with high infection risk. Cohort 3: adults > 65 years of age. Odds of having a PCV13 claim were calculated for each cohort. For Cohort 1, 78% out of a total of 353,214 subjects had a sufficient number of PCV13 doses to meet CDC recommendations. For Cohort 2, 3.7% out of a total of 673,157 subjects had a PCV13 claim. For Cohort 3, 18% of 1,262,531 subjects had a PCV13 claim. Odds of vaccination were generally lower in younger subjects, those with fewer outpatient claims, and those with residence in the Northeast and South regions. In Cohort 2, odds were reduced in subjects with generalized malignancy. Gender and urban residence were poor predictors of vaccination status. By understanding the demographic factors associated with lower rates of vaccination, clinicians may more effectively direct their efforts to increase pneumococcal vaccination coverage.