American Board of Internal Medicine (ABIM) Certification Practice Exam

How many doses of Tdap should be administered after hematopoietic stem cell transplantation?

1. 1 dose

2. 2 doses

3. 3 doses

4. No doses

The correct answer is: 3 doses

After hematopoietic stem cell transplantation, patients require revaccination due to the loss of immunity that occurs as a result of the conditioning regimen and the transplantation process itself. The Tdap vaccine, which protects against tetanus, diphtheria, and pertussis, is typically administered as part of this revaccination process. For individuals who have undergone hematopoietic stem cell transplantation, it is recommended that they receive a total of three doses of the Tdap vaccine. The vaccination schedule is generally as follows: the first dose can be given post-transplant, followed by a second dose at least a month after the first, and then a third dose at least six months after the second. This three-dose regimen helps ensure robust immunity against these infections as patients rebuild their immune systems. The other options of one, two, or no doses do not provide the full vaccination schedule needed to adequately protect these patients, thus emphasizing the importance of following the recommended three-dose course for effective immunization in this vulnerable population.