TYPHOID FEVER 85 



Thanks largely to the work of Wright, much has been 

 done to prevent infection with typhoid bacilli by pro- 

 tecting the individual through antityphoid vaccination. 

 For this purpose a bacterial vaccine is used, the typhoid 

 bacilli being very carefully killed by heat. The vaccina- 

 tion should consist of three injections a week apart. 

 The first one contains 500,000,000 bacilli, and the second 

 and third each 1,000,000,000. When lipo-vaccines are 

 used a massive dose is given in a single injection, not 

 repeated. 



The results of such protective antityphoid vaccinations 

 have been excellent; very few cases of typhoid fever 

 develop among those so vaccinated, and the cases that do 

 occur usually run a milder course. 



Treatment of developed cases of typhoid fever by means 

 of these vaccines or by specific sera has proved to be with- 

 out value. 



Inasmuch as experience has shown that now and then 

 infections resembling typhoid fever are due to paratyphoid 

 bacilli, protective inoculation is sometimes practised with 

 a so-called ''triple vaccine" consisting of typhoid bacilli, 

 paratyphoid bacilli type A, and paratyphoid bacilli 

 tj^pe B. As a rule the reactions from triple vaccine are 

 more severe than from the ordinary typhoid vaccine. 



