Inclusion/Exclusion Criteria:  Age >18 years. Diagnosis of CLL or SLL according to WHO criteria.  For patients receiving BTK inhibitor (Cohorts 1 and 2):  Patient must have no history of cytotoxic chemotherapy within 1 year (no prior history of bendamustine or fludarabine is permitted) and no history of CD20 monoclonal antibody within 6 months. Patient must have no known clinical or radiographic evidence of CLL progression.  For patients not on active therapy (Cohort 3):  Patient must have no history of cytotoxic chemotherapy within 1 year (no prior history of bendamustine or fludarabine is permitted) and no history of CD20 monoclonal antibody within 6 months. The treating investigator must have no intention to initiate CLL therapy within 2 months. Patients must have not received PCV13 within 2 years. For patients with PCV13 within 5 years, S. pneumonia IgG antibody concentrations must be less than the reference value for at least 50% of S. pneumoniae serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A,19F and 23F. Patients can have received prior PPV23 within any time frame. Patient must have no known history of HIV or primary immune deficiency disorder, nor be taking a concurrent immune suppressing medication (e.g. steroids, methotrexate, etc.).