To Örebro University

Patients with chronic lymphocytic leukemia (CLL) are at increased risk of Streptococcus pneumoniae infections due to disease- and treatment-related immune dysfunction. Vaccine responses are often impaired. This thesis evaluates the immune response to primary immunization with pneumococcal conjugate vaccine (PCV) versus pneumococcal polysaccharide vaccine (PPSV), long-term antibody persistence and the effect of revaccination in CLL patients.

Study I was a randomized trial in treatment-naïve CLL patients comparing PCV and PPSV, demonstrating that PCV elicits an enhanced immune response.

Study II was a prospective study evaluating B-cell subsets and plasmablast dynamics before and after revaccination. It showed that repeated revaccinations with PCV in CLL patients improves early humoral response.

Study III assessed antibody persistence 5 years after primary immunization and response to revaccination, showing that CLL patients have poor long-term antibody persistence, but that revaccination with PCV enhances immunity.

Study IV examined the impact of two analytical methods, multiplex immunoassay (MIA) and enzyme immunoassay (EIA), on serotypespecific IgG measurements and demonstrated their influence on vac-cine response interpretation in CLL patients. The findings in this thesis emphasize the importance of pneumococcal conjugate vaccines in CLL patients and suggest a need for revaccination to maintain protection against severe pneumococcal disease.