[Vaccination of adult patients receiving hematopoietic stem cell transplantation: Perspective of Costa Rica].

In this article the present recommendations for immunization of adult patients who received hematopoietic stem cell transplantation -a common procedure in therapy of many types of hematological diseases and serious inborn defects of the immune system- are reviewed and discussed. Patients that undergo this kind of transplantation procedure exhibit, compared to the general population, an elevated susceptibility of immune-preventable infections, due to loss of the humoral and cellular protective immunity. A revaccination strategy for transplanted patients can result in a significant diminution of morbidity and mortality related to the treatment of these diseases. Few data are published about the duration and magnitude of the vaccination response in this specific population of patients. Moreover, deviation from international guidelines recommendations for post-transplant immune prophylaxis can be observed frequently, partly as a result of the absence of specific vaccines in some countries. Multiple factors as intensity of the pharmacologic immune suppression, myeloablative regimen, administration of monoclonal and polyclonal antibodies, duration of the post-transplant period or the presence of graft-versus-host disease (GVHD), can influence the immune response and establish special considerations for certain biological agents, as observed in case of living attenuated virus composed vaccines. This conditions are responsible for the fact that an optimal time point for vaccination of transplanted patients remains not clearly defined. More specific studies about the underlying immunological mechanisms during immunocompromised periods are necessary to understand better the immunogenicity and security of existing vaccines. The development of innovative vaccines as well can induce certain advances in the post-transplant therapy.