PROPHYLACTIC IMMUNIZATION OR VACCINATION 649 



with the bacillus, and just preceding or directly after death they collect 

 the peritoneal exudate, in which the organisms are allowed to continue 

 growing for twelve hours more. The bacilli are then killed at a low 

 temperature, and the fluid thus obtained, after a preservative has been 

 added, constitutes the vaccine. 



Dosage. The ordinary dose of Haffkine's prophylactic for adult 

 males is from 3 to 3.5 c.c. ; for adult females, from 2 to 2.5 c.c. Haffkine 

 himself has injected larger quantities without resulting harm. He 

 recommends giving a second injection after from eight to ten days. 

 The injections are given subcutaneously, with a sterile syringe, into the 

 upper arm or elsewhere in areas where the skin is not tightly bound down. 



The local and constitutional effects are similar to those in typhoid 

 except that they are slightly intensified. The inoculation is followed 

 by redness and swelling at the seat of inoculation, and general symp- 

 toms in the form of rise of temperature and a feeling of illness. The 

 latter pass off in twenty-four hours, but the patient should rest during 

 the first day after inoculation. 



Duration of Immunity. The immunity is apparent a few days after 

 inoculation, but is of short duration. In India the protection is believed 

 to last at least three months and possibly longer. In times of epidemic 

 the inoculations should be repeated 'at least two or three times a year. 

 The brief duration of the immunity is probably one reason why better 

 results are not secured. Best results are observed during epidemics when 

 protection is afforded for a short time, or until the danger is past. In 

 countries or localities where the disease is endemic, persons may refuse 

 repeated inoculation and thus become susceptible to infection. 



Results. In the pneumonic variety of plague the prophylactic does 

 little or no good, a finding that has also been shown experimentally by 

 Strong and Teague. 1 



In the bubonic variety Haffkine's vaccine has in general yielded 

 encouraging results. The protection is not absolute; the immunity 

 is of relatively short duration, and therefore good results are not so 

 readily appreciated when the disease is endemic. The mortality among 

 the inoculated is much lower, i. e., 11 to 41 per cent., as compared with 

 50 to 92 per cent, among the non-immunized. Haffkine summarized 

 his results a few years ago as follows: Among 186,797 inoculated 

 persons there were 3999 attacks, or 1.8 per cent.; among 639,630 un- 

 inoculated persons there were 49,433 attacks, or 7.7 per cent., with 29,733, 

 or 4.7 per cent, of deaths. 



1 Philippine Jour. Sci., 1913, vii. 



