American Board of Internal Medicine (ABIM) Certification Practice Exam

What is recommended for varicella-zoster immunization for patients who are seronegative after hematopoietic stem cell transplantation?

1. 1 dose at transplantation

2. 2 doses after 12 months

3. 2 doses after 24 months if no GVHD

4. Not recommended under any circumstances

The correct answer is: 2 doses after 24 months if no GVHD

For patients who are seronegative after hematopoietic stem cell transplantation (HSCT), the recommended approach for varicella-zoster immunization is to administer two doses of the vaccine, typically starting after 24 months from the transplantation, provided there are no complications such as graft-versus-host disease (GVHD). This timing is crucial because the immune system typically begins to reconstitute and regain function around this period following HSCT. Administering the varicella-zoster vaccine too early, especially within the first year post-transplantation, may not elicit an adequate immune response. Hence, ensuring a 24-month interval allows the patient's immune system to sufficiently recover before vaccination, minimizing the risk of vaccine failure. Moreover, the presence of GVHD can complicate the post-transplantation immune response and may affect the timing and suitability of vaccinations. Therefore, for patients without GVHD, the two-dose schedule becomes a safe and effective strategy to ensure adequate protection against varicella-zoster virus.