TYPHOID BACILLUS 333 



The immunity produced is generally considered to be relatively 

 complete for from six months to a year. It must be remembered that 

 for at least three weeks following the vaccination there is a diminution 

 in the resistance of the individual to typhoid fever; consequently, 

 typhoid vaccination should not be undertaken if there is a possibility 

 of exposure to typhoid during this period. Vaccination is also very 

 undesirable if it is performed during the incubation period of typhoid 

 fever. It should be practiced only on perfectly healthy subjects free 

 from all general and local organic defects or infections, particularly 

 tuberculosis. Nurses, ward orderlies, doctors, and those engaged in 

 the care of typhoid patients are particularly likely to benefit by these 

 inoculations. Gay and Claypole 1 have demonstrated experimentally 

 that a satisfactory degree of protection may be attained in animals 

 by three injections, at intervals of two days each, of a dried sensitized 

 vaccine. Observations upon man immunized with this vaccine 

 indicate that the reactions are milder and the whole process can be 

 completed within a week, thus diminishing very materially the time 

 element which has been an important factor in the past. It is very 

 probable that the period of increased susceptibility to infection may 

 be decidedly shortened as well. 



Vaccination with Living Cultures. Metchnikoff and Besredka 2 

 found that the subcutaneous injection of living sensitized cultures 

 produced an immunity in anthropoid apes which was apparently 

 as definite as that produced by an actual attack of typhoid fever. 

 The organisms were shown not to appear in the urine or feces or blood 

 when introduced subcutaneously. They were unable to induce 

 immunity in the chimpanzee with killed cultures of typhoid bacilli 

 or with autolysates of killed cultures. Having in mind the efficiency 

 of living cultures, they 3 attempted the vaccination of man with living 

 cultures of the typhoid bacillus. They used sensitized cultures which 

 appeared to cause only a feeble local reaction and no general reaction 

 in the chimpanzee, in preference to non-sensitized living cultures, 

 which they found produced rather intense local and general reac- 

 tions. The vaccine was prepared by emulsifying agar cultures of 

 typhoid bacilli in normal salt solution and permitting the organisms 

 to remain in contact with antityphoid seri'm for twenty-four hours 

 at 37 C. The organisms are then removed by centrifuging, washed 



1 Loc. cit. 



2 Ann. Inst. Past., 1913, xxvii, 597. Besredka, Ann. Inst. Past., 1913, xxvii, 607. 



3 Semaine Med., July 24, 1912, 355. 



