This is a randomized controlled trial designed to assess the immunogenicity of the new pneumococcal conjugate vaccine in a cohort of allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients. This will be done by using an approach of pre-transplant donor immunization with post-transplant recipient immunization. Response will be compared with the standard 23-valent polysaccharide vaccine. It is hypothesized that the conjugate vaccine will provide an enhanced response in this group of immunosuppressed individuals who respond poorly to standard polysaccharide vaccines.