Persons living with HIV (PLWH) are at increased risk of chronic inflammation and the associated adverse health outcomes. There is considerable evidence that chronic inflammatory conditions like metabolic disease and autoimmune disorders are associated with weakened vaccine responses and existing vaccine studies in PLWH do not adequately sample older individuals who are disproportionately affected by this “inflammaging.” We hypothesize the effect of age on poor vaccine responses is greater among PLWH given the additional burdens of HIV driven inflammation. The overall project goal is to examine this premise by measuring the impact of HIV status, age, and chronic immune activation on conjugate pneumococcal vaccine responses. We will study acute (30 day) and longer-term (2 year) immune responses following PCV20 vaccination, among a cohort of participants including 4 groups: a) older PLWH, age ≥50 (n=100), b) older HIV uninfected controls, age ≥50 (n=50), c) younger PLWH, age <50 (n=50), d) younger HIV uninfected controls, age <50 (n=50). With these cohorts, we will 1) Comprehensively characterize the impact of HIV and age on the immunogenicity of conjugate pneumococcal vaccination by longitudinally tracking adaptive vaccine- specific antibody, B cell and CD4 T cell responses. We will compare these responses by age and HIV status. We will also 2) Determine the influence of chronic inflammation on vaccine-specific immunity among PLWH across the adult lifespan by measuring the associate between vaccine immunity and biomarkers of chronic inflammation. This project will provide valuable knowledge on how HIV and age influence vaccine immune responses with the hope of informing vaccine development and schedule to optimize the long-term health of persons living with HIV.