 This retrospective observational study analyzed PCV13 uptake among immunocompromised adults aged 19 to 64 years using insurance claims and electronic health records data from October 2011 to October 2016. The study found that four years after the ACIP 2012 recommendation, PCV13 uptake in high-risk adults aged 19 to 64 years was low at less than 15% in all overall analyses. This article was authored by Jeffrey Vitri, James Harnett, Bérel Emmer, and others.