Inclusion Criteria:  NAIVE COHORT: Subjects must have a confirmed diagnosis of chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) (collectively referred to as CLL throughout) according to the 2018 International Workshop on CLL. NAIVE COHORT: Male or female subject aged >= 18 years. NAIVE COHORT: Subjects must not have received prior therapy for CLL. VENETOCLAX-TREATMENT COHORT: Subjects must have a confirmed diagnosis of chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) (collectively referred to as CLL throughout) according to the 2018 International Workshop on CLL. VENETOCLAX-TREATMENT COHORT: Subjects must have received venetoclax (any dose) for at least 12 months with the last dose =< 12 months prior to registration.  Exclusion Criteria:  Subjects who have experienced and allergic reaction to prior vaccination. Subjects who have received a pneumococcal vaccination in the last five years. Active infection requiring topical or systemic therapy.  Current or prior use of immunosuppressive medication within 14 days of cycle one day one, EXCEPT for the following permitted steroids:  Intranasal, inhaled, topical steroids, eye drops or local steroid injection (e.g., intra-articular injection); Systemic corticosteroids at physiologic doses =< 10 mg/day of prednisone or equivalent; Steroids as premedication for hypersensitivity reactions (e.g., computed tomography [CT] scan premedication). Concurrent illness or condition, which, in the opinion of the treating investigator, would negatively impact the subject's study participation.