CHAPTER XIII 

 PNEUMOCOCCAL VACCINES 



The preparation of vaccines from pneumococci, their components, 

 or derivatives ; the use of vaccines in the prevention and cure of 

 pneumococcal infections; with a discussion of the theoretical and 

 practical factors involved. 



The very nature of pneumococcal disease would seem to pre- 

 clude the possibility of engendering by artificial means any 

 secure or lasting protection against invasion of the body by pneu- 

 mococci. The sudden onset, the often brief and stormy course, and 

 the abrupt termination of the disease, so dramatically exemplified 

 in lobar pneumonia in man, constitute a syndrome which results 

 only in a fleeting insurance against a second attack by the same 

 bacterial species. In diseases such as smallpox and anterior polio- 

 myelitis, the morbid processes are caused by toxins or by living 

 viruses, and specific stimulation of the immune mechanism usually 

 eventuates in lasting defense. In infections by Pneumococcus, how- 

 ever, the struggle is between the natural forces of the body and the 

 living cocci, and if the issue is successful on the part of the animal, 

 the body is left almost as defenseless against these same bacteria 

 as it was before the conflict. 



Therefore, it is unreasonable to expect that the administration 

 of pneumococci or of pneumococcal derivatives, no matter how art- 

 fully modified so as to be no longer capable of harm, would confer 

 upon the recipient more than a short period of freedom from sub- 

 sequent invasion by Pneumococcus. The attempts of immunolo- 

 gists to devise a suitable immunizing agent have been notable more 

 for their ingenuity than for their success in establishing an im- 

 mune state of high degree or of long duration. To be sure, there is 

 abundant experimental evidence, as has been presented in previous 

 chapters, that suitable antigens prepared from pneumococci and 



