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BACKGROUND/OBJECTIVES Vaccination against herpes zoster (HZ) is an effective strategy in protecting the population against consequences of varicella zoster virus reactivation. Optimal immunogenicity with recombinant zoster vaccine (RZV) relies on completion of the 2-dose series within 2-6 months from the first dose. The objectives of this study were to estimate RZV completion rates and adherence with the recommended administration schedule in the general United States population aged at least 50 years and to evaluate factors influencing completion rates. METHODS Longitudinal, open-source pharmacy and medical claims databases were analyzed for adults aged at least 50 years with a first RZV prescription filled between October 2017 and September 2019. The data were linked to Experian Marketing Services Consumer View data to obtain information regarding race. Completion rates and adherence were calculated overall and stratified according to claim source, age class, sex, and payer type. Logistic regression models were built for each subpopulation of interest to identify factors correlating with completion rates. RESULTS Overall, cumulative completion rates were 70.41% and 81.80% at 6 and 12 months, respectively. Median time to second dose was approximately 4 months (4.08-5.13 months) and adherence 67.62%. Completion rates were lower in the medical claims database compared with the pharmacy claims database (48.98% vs. 73.23% at 6 months). Regression models confirmed that pharmacy claim was an independent factor for higher completion rates, while African American race and Medicaid status were associated with lower completion rates. Most comorbidities, including chronic obstructive pulmonary disease and type 2 diabetes mellitus, were associated with lower completion rates. CONCLUSION Pharmacists contribute substantially to the overall high RZV completion rates in the United States. However, completion rates can be improved, especially in people receiving their first RZV dose at a physician's office. Future strategies should aim at lowering barriers to completing vaccination series in African Americans, Medicaid beneficiaries, and people with comorbidities.