Pneumococcal Pneumonia Vaccine Series (PCV20 and PPSV23) in Patients With Chronic Lymphocytic Leukemia Associated Immunodeficiency, PROTECT CLL Trial

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 pneumococcal vaccination.
* Subjects who have received a PCV13 or PCV20 pneumococcal vaccination in the last five years.

  * If they have received PPSV23 in ≥ 1 year and no other pneumococcal vaccine they may be included.
* Active infection requiring systemic antibiotic 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.