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

This study is testing the most effective pneumococcal vaccination strategy (against a common type of pneumonia) for patients with chronic lymphocytic leukemia (CLL) — a blood cancer that weakens the immune system — both in newly diagnosed untreated patients and in those who have been treated with venetoclax. **You may be eligible if:** - You are 18 years or older - You have been diagnosed with CLL or small lymphocytic lymphoma (SLL) - Either: you have never received treatment for CLL (naive cohort), or you have been on venetoclax treatment for at least 12 months and your last dose was within the past 12 months (venetoclax cohort) **You may NOT be eligible if:** - You have had a severe allergic reaction to a previous pneumococcal vaccine - You received a pneumococcal vaccine (PCV13 or PCV20) in the past 5 years - You have an active infection requiring antibiotics - You are currently on immunosuppressive medications (other than low-dose steroids or inhaled/topical steroids) Talk to your doctor to see if this trial is right for you.