PROPHYLACTIC VACCINATION 293 



pneumonia produced by fixed types, and these were all secondary to 

 severe attacks of influenza. This exclusion is justified by the fact that 

 protective bodies do not begin to appear in the serum until the eighth 

 day after injection of pneumococcus lipovaccine." " The pneumonia 

 incidence rate per 1000 men during the period of the experiment was 

 twice as high for unvaccinated recruits as for vaccinated recruits, and 

 nearly seven times as high for unvaccinated seasoned men as for 

 vaccinated seasoned men." The death rate for vaccinated men, in whom 

 the pneumonia developed more than one week after vaccination was 

 12.2 per cent., whereas among the unvaccinated troops it was 22.3 per 

 cent. The death rate for primary pneumonias wasi only one-third as 

 great among vaccinated men as among unvaccinated, but the rate in 

 pneumonia secondary to influenza was about the same for both groups. 

 Among the 20 per cent, of the command which were unvaccinated 327 

 cases were reported. These statistics were sufficiently encouraging to 

 introduce vaccination into the army on a fairly large scale. Neverthe- 

 less, the results are not sufficiently conclusive to state positively that a 

 high degree of protection is obtained. Recently Cecil and Blake have 

 been able to produce in monkeys a characteristic pneumococcus pneu- 

 monia by intratracheal inoculation. These investigators have studied 

 the problem of vaccination with saline vaccines and lipovaccines of 

 killed pneumococci and in addition have investigated the value of vac- 

 cination with living organisms. They found that vaccination with killed 

 pneumococci was not effective in preventing the development of the 

 disease under the conditions of infection but that the vaccinated animals 

 showed a somewhat less severe form of the disease. The living vaccine 

 was considerably more satisfactory, but they state that " the method 

 is too dangerous for any sort of practical application." Vaccination 

 with living virulent pneumococcus, Type I, produces a protective im- 

 munity against pneumonia of homologous types. The immunity against 

 other types of pneumococcus following vaccination with Type I offers a 

 certain degree of protection against other types, but this varies con- 

 siderably with the individual monkey. Vaccination with " living aviru- 

 lent pneumococcus Type I, if administered in sufficiently large doses, 

 renders the monkey immune to a subsequent pneumonia of homologous 

 type." Cecil and Blake point out that "vaccination with attenuated 

 living pneumococci could probably be practiced with impunity, but the 

 problem of transporting and keeping alive large quantities of pneumo- 

 cocci in the field would be difficult to solve." 



Vaccination Against Plague. Prophylactic vaccination against 

 plague was first reported by Haffkine in 1897. Subsequently Pfeiffer 

 and also Gaffky reported experiments which support the value of this 

 type of vaccination. Haffkine's vaccine was prepared from a killed broth 

 culture of the bacillus pestis five or six weeks old. Adult males were 

 given 3 to 3.5 c.c. and adult females 2 to 2.5 c.c. Kolle's vaccine is 

 prepared from slant agar growths suspended in the proportion of 2 mg. 

 of bacilli to the cubic centimeter of salt solution. Kolle and Strong 

 also employed living organisms whose virulence had been greatly re- 



