A Core will be established to support investigations on human subjects in the three research projects. This Clinical Subjects and Recruitment Core will provide a centralized resource for subject recruitment, screening and enrollment. Project 1 will focus on SARS-CoV-2 vaccination in adults with autoimmune disease in the Yale-New Haven Health system who have undergone B cell depletion therapy. While samples from primary vaccination have already been collected, a trial of repeat SARS CoV-2 vaccination and of influenza vaccination will be done. Project 2 recruitment will focus on recruitment of older (age ≥ 65) nursing home and senior assisted living residents for a randomized trial of high-dose versus MF59-adjuvanted influenza vaccine, and will also recruit young adults (age 21-39) as controls. Project 3 will recruit young adults (age 16-30) with sickle cell disease for studies of immune dysregulation and response to the pneumococcal polysaccharide vaccine, together with controls without sickle cell disease. The Core will also facilitate skin biopsies of the vaccination site and regional lymph node biopsies following vaccination in a subset of participants to assess tissue transcriptomic responses. This Core will also be responsible for ensure safety and information security for all participants and for compliance with all regulatory measures. The Core will be responsible for maintaining and deploying our established barcoding sample system for generation of subject numbers, tracking of samples, and mapping to external IDs, collaborating with Core B (Data Management and Analysis), where data management platforms are based. The Core is led by investigators with extensive experience carrying out human immunology studies who have the necessary regulatory and clinical experience. Consequently, this Clinical Subjects and Recruitment Core will advance the goals of this Human Immunology Project Consortium application.