American Board of Internal Medicine (ABIM) Certification Practice Exam

When should the Tdap vaccine be administered after hematopoietic stem cell transplantation?

1. 6 months after transplantation

2. Immediately

3. 3 months after transplantation

4. Before transplantation

The correct answer is: 6 months after transplantation

The Tdap vaccine is typically recommended to be administered 6 months after hematopoietic stem cell transplantation. This timing aligns with the need for the patient to have achieved adequate immune reconstitution following the transplant. After undergoing such a procedure, individuals often experience significant immunosuppression, which can compromise their ability to mount a proper immune response to vaccines. If the Tdap vaccine is given too soon after transplantation, when the immune system is still recovering, it may not be effective. Administering the vaccine 6 months post-transplant ensures that the patient's immune system has had enough time to recover, allowing for a better and more robust immune response to the vaccine. This is crucial for effective prevention against tetanus, diphtheria, and pertussis, which are particularly important in immunocompromised patients who may be at higher risk for these infections. Administering the vaccine immediately or shortly after transplantation would not provide the necessary immunity, as the immune system would likely not be able to respond adequately. Likewise, giving the vaccine before transplantation would not be appropriate, as patients would be entering a period of significant immunosuppression, which would negate the benefits of the vaccination that was administered prior to the procedure.