Pneumococcal Vaccine: A Tool for the Evaluation of the B-Cell Function of the Immune System

The pneumococcal vaccine has been developed to prevent infections caused by the most common of the pneumococcal serotypes. This review will describe the pneumococcal vaccine, its composition, recommended use, and current knowledge of the protective levels of antibody. In addition to the protective effects of the vaccine, however, a new use is becoming important. This new use of the vaccine takes advantage of the fact that bacterial polysaccharide antigens, in general, produce antibody which maintain a stable concentration over a long period of time. Since the half-life of immunoglobulins at best is 3 weeks, a constant level of antibody must result in continued biosynthesis at a rate equivalent to the loss incurred by catabolism. Any decrease in B-cell function which upsets the steady state would result in a lower level of antibody and/or a poorer response to immunization. It is this use of the pneumococcal vaccine, the measurement of antibody levels after immunization, which I term a tool for the evaluation of the B-cell function of the immune system. Composition of the 23-Valent Vaccine. Although pneumococci are exquisitly sensitive to chemotherapeutic and antibiotic agents, the work of Dr. Robert Austrian (1-5) has conclusively demonstrated that there is a significant mortality associated with pneumococcal infections despite prompt and adequate treatment. The inescapable conclusion therefore is the need for prevention of infection, hence a vaccine. That a vaccine is efficacious has been shown by the work of McLeod et al. (6) many years ago. More recent studies of the epidemiology of pneumococcal infections (2, 7-19) indicated that a limited number of pneumococci were responsible for the vast majority of infections. The first commercially available vaccines were discontinued with the advent of chemotherapeutic and antimicrobiol agents but recently a 14-valent vaccine was licensed (20).