VACCINATION 469 



period of reaction following inoculation and if the patient is in the incubation 

 period of the disease, the latter runs its ordinary course, though it would 

 appear that under such conditions the vaccine may have some favourable 

 influence on it. The immunity lasts for one year at least (Haffkine), and it 

 would appear to be more efficient and to last longer in Europeans than in 

 Hindus. Haffkine has inoculated some hundreds of thousands of individuals 

 with his vaccine. 



Jatta and Maggiora prepare a vaccine similar to that of Haffkine. Plague bacilli 

 are grown in very shallow layers of broth for 4 days : the culture is then heated to 

 65 C. and carbolic acid added. The dose is 1 c.c. 



Gosio grows the bacillus in a shallow layer of broth. The growth is precipitated 

 with a powerfully agglutinating serum, collected, made into an emulsion and 

 sterilized by heating at 65 C. for an hour. (To ensure the sterility of the vaccine 

 a little is sown in broth containing potassium tellurate (1 part in 100,000) ; if the 

 vaccine be sterile the appearance of the broth remains unchanged, if on the other 

 hand blackish flakes appear in it then the sterilization is imperfect.) Each c.c. of 

 culture yields about 1 mg. of vaccine of which the vaccinating dose for an adult 

 man is 2-3 mg. (2-3 c.c. of emulsion). In this vaccine the antiserum merely plays 

 a mechanical part in precipitating the bacilli ; its antitoxic properties are destroyed 

 at the temperature (65 C.) at which the vaccine is sterilized. 



The German Plague Commission (Gaffky, Pfeiffer, Sticker and Dieudonne) 

 proved the superior efficacy of vaccines prepared from cultures on solid 

 media. 



The bacillus is sown on agar in Roux bottles, and incubated for 3 days and the 

 growth scraped off. The emulsion is then heated for three-quarters of an hour 

 at 65 C., and sufficient sterile normal saline solution added to make the total volume 

 up to 200 c.c. for the growth from each bottle. The emulsion is distributed into 

 tubes, sealed and heated a second time to ensure its sterility. One c.c. contains about 

 2 '5 mg. of bacilli. 



The German vaccine has been used for the inoculation of 200,000 Japanese. 

 A similar vaccine, prepared at the Manguinhos Institute, Rio de Janeiro, has 

 proved of considerable value in Brazil. 



(ii) With living attenuated cultures. In some old agar cultures of the 

 plague bacillus, Yersin and Carre found a number of colonies of an attenuated 

 bacillus (Race 6) which only proved fatal to 20 per cent, of rats inoculated 

 and in the other cases afforded immunity. Yersin inoculated himself with 

 this attenuated virus and merely suffered from a slight febrile attack. 



Kolle and Otto proposed to use as a vaccine a bacillus of low virulence 

 attenuated by growing it at 40 41 C. This virus is not fatal to guinea-pigs 

 when inoculated in quantities of two loopsful sub-cutaneously, and produces 

 an immunity lasting several months in guinea-pigs and rats. On these data, 

 Strong has shown that any plague bacillus which does not kill guinea-pigs 

 (250 grams) when a whole agar tube culture is inoculated sub-cutaneously 

 can be used as a vaccine, and he has inoculated 200 persons in the Philippines 

 each with a tube of such a culture without producing any disturbance of 

 health. 



(iii) With heated exudates. Terni and Bandi use the heated peritoneal 

 exudate of a plague-infected guinea-pig as a vaccine. This method of vaccina- 

 tion is said to give a high degree of immunity in a short space of time and to 

 produce a merely insignificant reaction. It has up till now been little used 

 in practice though a few hundred persons were inoculated at Rio de Janeiro. 



A culture of a virulent plague bacillus is inoculated into the peritoneal cavity of 

 a guinea-pig, and when the animal is in extremis it is killed. The peritoneal exudate 

 is collected, and diluted with a little normal saline solution ; the mixture is incubated 

 for 12 hours at 37 C. and then heated at 50 C. for 2 hours on two consecutive days. 



