American Board of Internal Medicine (ABIM) Certification Practice Exam

When should MMR vaccination occur following hematopoietic stem cell transplantation, provided there is no GVHD or immune suppression?

1. Immediately after transplantation

2. 6 months after transplantation

3. 24 months after transplantation

4. 12 months after transplantation

The correct answer is: 24 months after transplantation

Following hematopoietic stem cell transplantation, the timing of the MMR (measles, mumps, rubella) vaccination is crucial for ensuring adequate immunological response and protection against these diseases. In the absence of graft-versus-host disease (GVHD) or ongoing immune suppression, the recommendation is to administer the MMR vaccine 24 months after transplantation. This duration allows sufficient time for the recipient's immune system to recover and reach a state where it can produce an appropriate immune response to the live attenuated vaccine. Vaccination before this period may not confer adequate immunity, as the immunosuppressive effects of the transplant can interfere with the body's ability to respond to live vaccines. Additionally, certain types of immunosuppressive therapy or the presence of GVHD could further necessitate delaying vaccination. The other time frames listed, such as immediately, 6 months, or 12 months post-transplantation, would not provide the optimal recovery period for the patient's immune system to respond effectively to the MMR vaccine. Thus, the recommendation of 24 months is based on clinical guidelines and evidence that this timing maximizes vaccine efficacy and patient safety.