68 
BACTERIOLOGY. 
Produc¬ 
tion of 
immunity 
by vac¬ 
cines 
Quite recently the prevention of typhoid has been 
greatly advanced by what is known as vaccination. 
As mentioned earlier in the chapter, the poison of the 
typhoid bacilli is found "within the body of the cells, 
and is liberated only after death and disintegration of 
the organisms. An active immunity to the disease can 
be produced by injecting the killed typhoid bacilli, 
which after disintegration set free their poisons in the 
blood and stimulate the organs and tissues of the body 
to form protective substances that prevent infection. 
The inoculations consist of three injections of vaccine, 
the first one of 500,000,000, the last two of 1,000,000,- 
000 bacilli at intervals of one week. The vaccine most 
used is one containing both the paratyphoid and ty¬ 
phoid bacilli. The inoculations are sometimes followed 
by a reaction marked by a rise in temperature, head¬ 
ache, and general malaise. This method of creating 
immunity to typhoid has been practised a great deal 
in the last two years with very gratifying results. 
It was first tried in this country in the U. S. Army 
maneuver camp at San Antonio, Texas; 8097 men 
were vaccinated, that is, they were injected with a 
killed culture of typhoid bacilli on three occasions, the 
dose being increased each time. Only one case de¬ 
veloped among these men, and this one was not fatal. 
Among nurses and hospital attendants the anti¬ 
typhoid vaccination is being largely practised. In the 
Massachusetts General Hospital 1381 nurses and at¬ 
tendants were vaccinated with no cases of typhoid de¬ 
veloping subsequently. 
