This phase II trial compares the effect of initial vaccination (PCV20 followed by PSV23) with yearly vaccinations of PSV23 to the standard 5 year vaccination in patients with chronic lymphocytic leukemia. At present chronic lymphocytic leukemia patients are poorly protected by anti-pneumococcal vaccination. Current vaccination schedule for chronic lymphocytic leukemia patients is based on general recommendations in immunocompromised patients (initial vaccination with PCV13 followed by one dose of PSV23 after an interval of two months, followed by revaccination at 5 years). Giving patients frequent immunization as compared to 5 year immunization may result in higher protective titers in patients.