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Hematopoietic stem cell transplant is the infusion of blood-forming stem cells from a donor into a patient who has received high-dose chemotherapy and/or radiation. The transplant is generally classified as either autologous (the recipient receives back his own stem cells) or allogeneic (stem cells from a donor other than the recipient).
During the transplant process, immune deficiency is caused by the chemo and/or radiation preparation, which is damaging to the bone marrow, and in the case of allogeneic transplant, by the possibility of graft vs. host disease (GVHD) and the immunosuppressive drugs used to prevent and treat it. GVHD occurs because the unrelated donor cells recognize the recipient’s cells as foreign and attack them. GVHD can vary in severity and can be acute or chronic in nature.
In both types of transplant, all recipients rapidly lose their T- and B-lymphocytes and thus the immunity they have acquired through a lifetime of exposure to infection-causing organisms, environmental agents, and vaccines. Generally, autologous transplant patients will recover their immune systems more rapidly than allogeneic transplant patients. Despite the differences between the two transplant types, the risks of infection are quite similar and thus similar vaccination schedules are used for both. The immunization response is usually poor during the first 6 months after transplant and should not be attempted during this period.
Vaccines to be considered for stem cell transplant recipients are based on several considerations. Certain infections, such as those due to Streptococcus pneumoniae, Haemophilus influenzae type B, and influenza virus, are more frequent and more severe in transplant patients. The risk of side effects is another important factor--vaccines composed of live organisms have the potential to cause serious disease in transplant patients and should not generally be used, except in special conditions. In addition, travel to, or residence in, an area of endemic disease is a major concern.
There are slight variations in the recommendations made by the Centers for Disease Control (CDC) in Atlanta and by the European Group for Blood and Marrow Transplantation (EBMT). The following are routine vaccinations recommended for adult stem cell transplant patients:
1. Haemophilus influenzae type B conjugate - CDC recommends vaccination at 12, 14, and 24 months after transplant. EBMT suggests 3 doses starting at 6 months after transplant, with subsequent doses 1-3 months apart.
2. Streptococcus pneumoniae (pneumococcal) 23-valent polysaccharide - CDC suggests administration at 12 and 24 months after transplant. EBMT recommends 1 dose at 12 months post-transplant.
3. Diphtheria/tetanus toxoid - CDC suggests 3 doses at 12, 14, and 24 months after transplant. EBMT suggests 3 doses starting at 6-12 months after transplant with subsequent doses 1-3 months apart.
4. Influenza - Both CDC and EBMT recommend life-long seasonal inactivated vaccine (shot), beginning 6 months after transplant. Vaccination of family members and close contacts is also recommended.
5. Hepatitis B - CDC recommends 3 doses at 12, 14, and 24 months post-transplant for those patients at risk of disease (such as dialysis patients). EBMT recommends vaccination starting at 6-12 months after transplant with subsequent doses 1-3 months apart for recipients who are at risk, or who reside in countries where policy recommends vaccination of the general population.
6. Polio - CDC suggests 3 doses of inactivated vaccine (shot) at 12, 14, and 24 months post-transplant. EBMT recommends 3 doses of inactivated vaccine starting 6-12 months after transplant with subsequent doses 1-3 months apart.
7. Measles/Mumps/Rubella - Both CDC and EBMT suggest administering this vaccine at 24 months after transplant only for patients who are no longer immunocompromised and who do not have GVHD.
For those patients with unusual situations, such as specific disease exposures or residence in or travel to areas of endemic disease, consultation with an expert is recommended.
These current recommendations will be subject to change, since it is expected that the increase in stem cell transplantation will lead to more and better research on post-transplant immunization. One possible future approach includes a heat-inactivated varicella vaccine for chickenpox and shingles that is currently being evaluated; if proven safe and effective, it will probably be added to the immunization schedule. Another promising avenue is the use of granulocyte-macrophage colony stimulating factor (GM-CSF) that, administered with the hepatitis B and influenza vaccines, appears to result in higher levels of protection. More research will also occur on the use of vaccinations in transplant donors prior to donation, as it is possible that some protective immunity can be transferred to the recipients at an early period in the process.
Special Thanks to Sue herms of the IWMF for allowing permission to post this information |
