Adult vaccination rates in the United States are consistently lower than the National Healthy People 2020 goals. Barriers to adult vaccination include inconsistency of insurance coverage of adult vaccines and difficulty in accessing vaccines. To help address the gap in adult access to vaccines, in 2016 the Department of Health Care Services--which administers the Medi-Cal program (California’s version of Medicaid)--implemented the All Plan Letter (APL) 16-009, which requires coverage of recommended adult vaccines as a pharmacy benefit. Adult Medi-Cal patients can now receive the vaccines recommended for their age and underlying health conditions, and they can do so not only at a provider’s office but also at local pharmacies, improving access and convenience. This policy brief recommends expanding coverage of all adult vaccines as a pharmacy benefit of all public and commercial insurance plans.