Follow-up of Vaccination Status in Adults after Allogeneic Hematopoietic Stem Cell Transplantation

Background. Following hematopoietic stem cell transplantation (HSCT), the  probability that acquired protective immunity is lost over time is significant. Therefore, a systematic reimmunization is important to re-establish appropriate immunity and to decrease the risk of vaccine preventable infectious diseases with their related morbidity and mortality. The aim of this study is to investigate whether the recommendations for vaccination were followed in our hospital and to which extent of conformity they were used.

Methodology. A 2-year retrospective survey, including adult allogeneic HSCT patients, (transplanted) at the Ghent University Hospital, Belgium, who were at least 3 months post transplant. Administration of the first dose of conjugated polysaccharide vaccine against Pneumococci was studied.

Results. Data on vaccination schedules of 50 allogeneic transplantations were collected. Of these, 34 patients (68,0%) were eligible for recommended vaccinations. Patients were vaccinated on-schedule (i.e. time-frame between HSCT and vaccination as recommended in the hospital guideline) in 76,5% (26/34). Postponed vaccination with a medical indication was observed in 8,8% (3/34) of patients. Of them, 66,7% (2/3) were postponed because of infection and 33,3% (1/3) because of significant thrombocytopenia.

Postponed vaccination without a medical excuse was observed in a minority of the patients, i.e. 11,8% (4/34), with either ‘no medical reason’ in 75,0% (3/4) or nonadherence in 25,0% of patients (1/4). Postponed vaccination with initial medical indication but then followed by non-medical reason was observed in 2,9% (1/34) of patients. Vaccination data were not available for 32,0% (16/50) of patients. The reasons were death before start of vaccination in 75,0% (12/16), graft failure in 12,5% (2/16) and lack of information in 12,5% (2/16) of patients.

Conclusion. The results emphasize the need for close follow-up of post-transplant patients in our hospital. This is confirmed by satisfactory concordance between the hospital recommendation and vaccination of HSCT patients. Health-care providers play a crucial role by effectively and appropriately following the vaccination schedules. Moreover, literature data demonstrate  that actively involving the patient in the follow-up (e.g. providing them with their vaccination schedule) results in improved follow-up. The role of a personalized electronic alert system will be explored in near future. In addition, the appropriate follow-up of out-patient vaccination, 1 year after HSCT, will be studied.