People who have received an allogeneic hematopoetic stem cell transplant (HSCT) are more likely than other people to get ill from a germ called Streptococcus pneumoniae. Most people who have had a stem cell transplant are offered a vaccine called 23-valent pneumococcal polysaccharide vaccine (23vPS) to help protect against this germ. The purpose of this study is to evaluate the immune response in HSCT recipients who receive a 13 valent pneumococcal vaccine (13vPnC) followed by 23vPS.