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 a severe allergic reaction to prior pneumonia 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.