CHOLERA VACCINE 445 



the commissions sent to investigate the method were 

 unfavourable. 



Haffkine subsequently prepared a vaccine against 

 cholera from cultures of the Koch vibrio, which seems 

 to be efficacious in preventing the disease. For example, 

 a number of labourers were inoculated during an epidemic, 

 and among the inoculated the mortality was only 2-25, 

 whereas among the uninoculated it was nearly 19 per cent. 

 In another instance amongst 654 uninoculated there were 

 71 deaths, a mortality of 10-86 per cent., while among 

 402 inoculated there were only 12 deaths, a mortality of 

 2-99 per cent., and a reduction in mortality of 72-47 per 

 cent. 



In the Haffkine method two vaccines are made use of. 

 The first or weak vaccine is prepared from cultures of the 

 cholera vibrio attenuated by growing on the surface of 

 agar, with free aeration, for several generations. The 

 second or strong vaccine is prepared by enhancing the 

 virulence of a cholera culture by a succession of passages 

 through the peritoneal cavity of guinea-pigs. The viru- 

 lence of this culture must be maintained in the same 

 manner. 



For making both vaccines, " standard " agar cultures 

 are employed. These are tubes in which the sloping 

 surface of agar measures 15 cm. in length, and the cultures 

 are incubated for twenty-four hours. The whole growth 

 on such a tube is emulsified in 8 c.c. of broth or salt solu- 

 tion ; the dose of this is 1 c.c., and the living vaccines are 

 injected into the flank, the second or strong being given 

 seven to ten days after the first or weak. Haffkine 1 in 

 a recent study on cholera inoculation suggests the use 

 of the strong vaccine " devitalised." The devitalised 

 vaccine may be prepared by two methods, (a) prolonged 

 cultivation in broth and treatment of the culture with 



1 Preventive Inoculation against Cholera (W. Thackcr & Co., 1913). 



