Antibody titers to vaccine-preventable diseases decline during the 1-4 years after HCT, if the recipient is not revaccinated. HCT recipients are at increased risk for certain vaccine-preventable diseases, including those caused by encapsulated bacteria. In short, all HCT recipients should begin revaccination with inactivated vaccines 6 months after HCT. Three doses of pneumococcal conjugate vaccine (PCV) should be given 6 months following transplant followed by a dose of pneumococcal polysaccharide vaccine (PPSV) at least 8 weeks later. HCT recipients should receive 3 doses of Hib vaccine starting 6 to 12 months after successful transplant, regardless of vaccination history; doses should be administered at least 4 weeks apart. Immunocompetent people should receive MMR vaccine 24 months after transplant. For a complete discussion of the indications and schedule of vaccination, refer to the sub-section on recipients of HCT in the Altered Immunocompetence section of ACIP’s “General Best Practices Guidelines for Immunization” available at www.cdc.gov/vaccines/hcp/acip-recs/general-recs/immunocompetence.html.