Infection prevention by vaccinations in immunocompromised patients

Central to this thesis is the immunocompromised patient (ICPs) and infection prevention by vaccinations in these patients. ICPs are recognized as being at an increased infection risk; however, a key question is whether this also holds true for pneumococcal infections. We therefore studied the incidence rate of invasive pneumococcal disease (IPD) in ICPs and demonstrated that this rate is increased.
With regard to vaccine immunogenicity, we showed that immunosuppressive medication in patients with autoimmune disease mitigated the response to both pneumococcal conjugate vaccine (PCV) and pneumococcal polysaccharide vaccine (PPSV). Immunosuppressive medication in patients with inflammatory bowel disease mitigated the response to the sequential pneumococcal vaccination schedule with PPSV administered two months after administration of PCV. At last, we showed that nearly 15% of HSCT recipients did not reach seroconversion after pneumococcal vaccination.
In the second section of this thesis, we studied vaccination recommendations and other recommendations for travelling ICPs. We demonstrated that antibody concentrations after hepatits A or B vaccination were not measured in nearly 45% and 25% respectively, of ICPs with an indication for such a measurement. Half of all travelling ICPs in a specialised travel clinic did not receive a prescription of on-demand antibiotics, while these were actually indicated. This was an important finding, since we also demonstrated that travelling ICPs tended to have more frequent, and more severe travel-related health problems compared to immunocompetent travellers.
The findings and conclusions of this thesis support existing vaccination recommendations for ICPs with scientific evidence, and contributed to their improvement.