Influenza vaccination rates remain suboptimal. In a retrospective study including more than 31 million Medicare beneficiaries >19 years of age in the United States during the 2018 to 2019 influenza season, vaccination claims were filed for only 50 percent of individuals. Vaccination uptake was higher among White beneficiaries than Black or Hispanic beneficiaries (53, 35, and 30 percent, respectively), and was higher for those with high-risk conditions than for those without (56 versus 27 percent, respectively). Among unvaccinated beneficiaries overall, 77 percent visited a provider during influenza season. A comprehensive strategy leveraging all opportunities for vaccination is needed to improve influenza vaccine uptake.