Overview Impact of Metformin on Immunity Status: Active, not recruiting Trial end date: 2021-12-31 Target enrollment: Participant gender: Summary To determine whether metformin (MET) can improve the immune response to the pneumococcal conjugate vaccine (PCV-13) in older adults. Phase: Phase 1 Details Lead Sponsor: The University of Texas Health Science Center at San AntonioTreatments: Metformin