Abstract
The aim of this prospective study was to characterize the humoral immune response to TBE vaccination after hematopoietic stem cell transplantation (HSCT). Nineteen adult patients 11–13 months after HSCT and 15 age-matched immunocompetent adults received up to three TBE vaccinations. Antibodies against TBE virus were measured by neutralization test (NT). As primary endpoint, the antibody response (NT titer of ≥10 and at least a twofold increase from baseline 4 weeks after second vaccination) was compared between patients and controls using Fisher exact test. Prior vaccination, 15 (79%) HSCT patients still had detectable neutralizing antibodies. At primary endpoint, the antibody response was significantly lower in patients than in controls (35% versus 93%; p < 0.001). The CD4+ cell count was a predictor for an antibody response in patients (p = 0.019). Interestingly, the majority of HSCT patients still had detectable antibodies prior vaccination. Following vaccination, antibody response in HSCT patients was associated with the CD4+ cell count.
Highlights
Allogeneic hematopoietic stem cell transplant (HSCT) and marrow graft recipients experience an increased risk for infections due to delayed immune reconstitution, immunosuppressive therapy, and graft-versus-host disease (GvHD)[1,2]
Recent guidelines suggest re-vaccination against tickborne encephalitis (TBE) after allogeneic HSCT in endemic areas[5], the evidence for this recommendation is based on studies with other immunocompromised patient cohorts, more precisely with heart transplant recipients[19]
No data existed regarding the optimal time after HSCT when TBE vaccination can be expected to induce a sufficient immune response[4]
Summary
Allogeneic hematopoietic stem cell transplant (HSCT) and marrow graft recipients experience an increased risk for infections due to delayed immune reconstitution, immunosuppressive therapy, and graft-versus-host disease (GvHD)[1,2]. Guidelines recommend complete re-immunization against vaccine-preventable diseases after. Considering that lymphocytes need several months before they are mature enough to produce an effective vaccine response, the right timing after HSCT is difficult to determine. The effects of GvHD and immunosuppressive treatment might delay the process of immune reconstitution and limit the effectiveness of vaccination[2]. Recent guidelines recommend starting with vaccination against influenza, pneumococcal infection, and Haemophilus influenzae type b as early as 3 months after HSCT irrespective of whether the patient has or has not developed GvHD7.
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