[Vaccinations for immunocompromised hosts – focussing on patients after a hematological stem cell or organ transplantation, with HIV or with functional or anatomical asplenia].

Patients with an acquired immune deficiency, for example due to HIV-infection, after a solid organ or haematological stem cell transplantation or due to functional or anatomical asplenia, have a greater risk to experience severe complications or a chronic course of infection compared to healthy individuals. Vaccinations would pose an ideal primary preventive method. However, their efficacy is reduced if applied during the immunosuppressed period. Therefore, whenever possible, vaccinations should be administered before the period of immunosuppression starts – or caught up later during the period of minimal possible immunosuppression. Nevertheless, the benefit conveyed through vaccines is undisputed, particularly if indications regarding dosing of vaccines (amount and frequency of doses) are optimized according to the given state of immunosuppression. Live attenuated vaccines are contraindicated during severe immunosuppression. Serologies should still be analysed and documented however, since these vulnerable patients require passive immunization through specific or standard intravenous immunoglobulins in case of relevant exposure to the respective antigens. For all patients therefore, careful documentation and communication of previous vaccinations and serologies (protective or not) among the various medical specialties is required to optimize patient management. For all immunosuppressed patients the efficacy of polysaccharide vaccines (such as the pneumococcal and meningococcal vaccines PSV-23 and MPV-ACWY) is strongly reduced compared to the conjugated ones (PCV13 and MCV-ACWY). Therefore, contrary to most other national guidelines, the Swiss guidelines recommend to use only the conjugated versions in primary vaccination series as well as in boosters – this applies strongly for immunosuppressed patients, but is recommended also for the general population in Switzerland. Another common management recommendation specific for transplant patients is the indication to control vaccine efficacy by measuring titers. This is also indicated for hepatitis B in HIV-positive patients, but not required for any vaccine in asplenic patients. In summary, vaccines pose an important opportunity for primary and secondary prevention for vulnerable patients at highest risk of experiencing the worst forms of the diseases to be prevented.