646 ACTIVE IMMUNIZATION 



A comparison of these tables shows that the general reaction is much 

 more infrequent or milder in children than in adults, even after the first 

 dose; after the second and third doses the difference is more marked. 



In former years considerable stress was laid upon the possibility of 

 a negative phase following the inoculation, during which a person was 

 believed to be more susceptible to infection. This is now believed by 

 Leishman, Russel, and others of extended experience to be incorrect, 

 the more general belief being that inoculations may be made and are 

 especially indicated during epidemics of the disease. 



Duration and Degree of Typhoid Immunity. It should be empha- 

 sized that immunity following typhoid immunization is not absolute, 

 and an immunized person cannot afford to neglect ordinary precautions 

 against infection. A lowered state of general body health or a large dose 

 of infectious material may at any time result in infection. 



The prophylactic treatment should be used in conjunction with 

 well-known sanitary precautions in order to obtain the best results. 



The immunity is apparently manifest soon after the first and second 

 doses have been given. The duration is not known definitely. From 

 the rich experience of the British army in India Colonel Firth 1 concludes 

 that immunity begins to decline in about two and one-half years after 

 inoculation. However, even after four and five years the typhoid rate 

 among the inoculated is, estimated roughly, one-fourth that of unpro- 

 tected troops. 



Results. The value of the typhoid prophylactic therapy is best 

 shown in the army, where conditions are better controlled than is possible 

 in civilian life. In 1911, of a division of United States troops, about 

 20,000 men along the southern boundary, only two cases of typhoid 

 fever developed and both recovered. During this same period of time 

 49 cases were reported in the city of San Antonio, with 19 deaths. The 

 soldiers mixed freely in the city, ate of fruits and vegetables, drank of 

 the same water, and in this manner were freely exposed, although the 

 sanitary conditions in the camp were excellent. 



In 1898, during the Spanish War, there were assembled at Jackson- 

 ville, Florida, 10,759 troops, among whom there were certainly 1729 

 cases of typhoid, and including the suspected cases, this figure reached 

 2693 cases, with 248 deaths. This camp continued about as long as 

 that in 1911, the climatic conditions and water supplies being practically 

 the same, but the sanitary conditions were bad. The remarkable dif- 

 ference in the typhoid rate cannot, however, be reasonably explained by 

 1 Jour. Roy. Army Med. Corps, 1911, xvi, 589. 



