486 INFECTION AND RESISTANCE 



We have mentioned in another place that Metchnikoff and Bes- 

 redka in their studies on typhoid vaccination in the chimpanzee 

 have concluded that very little protective value resided in vaccina- 

 tion with dead typhoid vaccines, whereas animals vaccinated with 

 small amounts of living cultures were very efficiently protected. 

 Metchnikoff and Besredka adopted finally the method of immunizing 

 with living sensitized vaccines. By this is meant typhoid bacilli that 

 have been exposed to the action of heated immune serum, or, in 

 other words, typhoid bacilli that have absorbed specific antibodies. 

 There is no question as to the efficiency of this form of vaccination. 

 The method of employing sensitized bacteria for these purposes 

 utilized by Besredka in the case of plague has unquestionably won 

 an important place in active immunization. However, the results 

 of Russell and others seem to indicate that in human beings the use 

 of dead vaccines is certainly of considerable value, and there are 

 certain practical objections to the use of living vaccines in immuniza- 

 tion of large numbers of people as in armies to which Russell calls 

 attention. In the first place, living vaccines cannot be stored for 

 any considerable period, and may become a source of possible infec- 

 tion by mouth if carelessly handled; furthermore, contamination is 

 not so easily ruled out in the case of living vaccines when used on 

 a large scale, and it is not possible at present to require compulsory 

 vaccination with living bacteria. The choice of strains is important. 

 For vaccines in the British and American armies the Rawlings strains 

 usually used by Wright are employed at present. The work of Weiss, 

 Hooker and others recently has shown that perhaps we may have to 

 Ude for best results a polyvalent typhoid injection, and that in im- 

 munizing with paratyphoid B, a polyvalent vaccine will be necessary 

 eventually. The paratyphoid A strains are so uniform antigenically 

 that this will be unnecessary in their case. 



Gay has recently recommended the use of sensitized killed vac- 

 cines. He controls the efficiency of his vaccines by testing them out 

 on rabbits in which typhoid septicemia has been produced by inocu- 

 lation with cultures grown on rabbit blood agar. These vaccines have 

 not yet been used upon sufficient numbers to justify conclusions. It 

 would seem, however, that any one of the methods mentioned must 

 possess considerable value, since they all represent merely slight 

 variations of the same procedure. The method at present used in 

 the German, British, and American armies, namely, vaccination 

 with dead cultures, seems certainly, according to Russell's statistical 

 studies, to have yielded excellent results and recommends itself by 

 its extreme simplicity and safety. 



THERAPEUTIC VACCINE TREATMENT IN TYPHOID FEVER 



A number of workers have attempted to treat typhoid fever after 

 it occurred with typhoid vaccine sensitized and unsensitized. 



