194 ANTIGENS AND THE TECHNIC OF SERUM REACTIONS 
Bacterial vaccines are used rather widely both for prophylactic and 
curative purposes in specific acute infections. The list of these diseases 
in which vaccines have been tried is a rather long one, but the group 
in which unequivocal benefit has been derived is at present small. In 
some instances, particularly in the common cold and epidemic influ- 
enza, lay opinion has been frequently favorable, but this is at best an 
uncertain substitute for well-substantiated clinical data. 
Typhoid, Paratyphoid and CAo/era.— Prophylactic vaccination, 
especially to induce immunity to typhoid, paratyphoid alpha and 
beta, and to a lesser extent, cholera infections, has been very successful. 
Usually a vaccine containing a billion each of the four microbes to the 
cubic centimeter is prepared, and three doses are given at six-day inter- 
vals; 0.5 cc. for the first injection, and 1 cc. for each of the two following 
injections. A reaction follows the first, or less commonly the second 
injection in about 10 per cent of cases. This may be very mild, and 
transitory, or rather marked with a distinct chill, fever, and general 
malaise. Immunity lasts from two to three years on the average. 
The remarkable reduction of typhoid in the American and British 
armies since the introduction of prophylactic typhoid vaccination is 
ample demonstration of the effectiveness of the method. 
Therapeutic vaccination against typhoid and paratyphoid fever is 
much less convincing in its results. In those cases free from pneumonia 
or cardiac involvement, and which have no symptoms of hemorrhage, 
even the intravenous injection of reduced numbers of typhoid bacilli 
has been without obvious harm, and an occasional case has seemed to 
be distinctly improved. In general, however, the therapeutic value of 
typhoid, paratyphoid and cholera vaccines is still a matter of doubt. 
Plague.— The use of vaccines as prophylactic agents in plague has not 
been as striking as the use of typhoid vaccines for the prevention of 
typhoid fever, but some favorable results have been reported, both with 
respect to reducing the incidence of plague in epidemic areas, and in 
modifying the course of the disease favorably in vaccinated persons. 
DyseiUery .—Dysentery vaccines have not been successful; the Shiga 
type of dysentery bacillus is so toxic it is difficult to prepare suitable 
vaccines. 
Pertvssis.—VeTtussis vaccines have been used by a number of 
observers. In general they seem to afford some degree of protection, 
but are on the whole relatively ineffective therapeutically. 
Influenza and Epidemic hifliienza .—Yaccmes have been used very 
extensively, especially during the last epidemic of influenza. The 
results were on the whole very disappointing. 
