Expanding Options for Preventing Invasive Pneumococcal Disease: The Old Conjugate Vaccine Made New Again

use of the pneumococcal 13-valent conjugate vaccine (Prevnar 13®, Pfizer, Inc.) for adults 50 years of age and older. This approval was based on the measured immune responses and observed safety profile of the vaccine and not on controlled trials in adults actually demonstrating a decrease in pneumococcal invasive disease. Those trials are ongoing currently and so a recommendation that it be given to all adults 50 or over has yet to be made. In the world of immunocompromised transplant patients, the use of a conjugate pneumococcal vaccine is somewhat intriguing. The vaccine includes the most common serotypes to cause disease: 4, 6B, 9V, 14, 18C, 19F, and 23F (similar to the previously recommended 7-valent conjugate pneumococcal vaccine in children), as well as six new additional serotypes: 1, 3, 5, 6A, 7F and 19A. Although this may not be as many as the currently widely used 23-valent polysaccharide pneumococcal vaccine (Pneumovax®, Merck, Inc.), the mechanism of immune stimulation is different and has potential benefits. Since polysaccharides from bacterial capsids are not always immunogenic, the conjugate vaccines utilize an inactivated Diphtheria protein coupled to the pneumococcal polysaccharide subunit in order to activate helper T cells and produce more high affinity antibodies against the polysaccharides. Memory B cells made from this process then, i