SERUM TREATMENT OF DIPHTHERIA 771 



of the previous introduction of diphtheria bacilli (carriers), which latter 

 render the individuals hypersensitive to the T.-A. Reactions that are 

 regarded as non-specific have been observed in tuberculous and scrofu- 

 lous persons, and for the present von Behring prefers that the use of the 

 prophylactic in such persons, as well as in atrophic infants and infants 

 less than nine months old, be regarded as contraindicated. 



The fear expressed by some that the prophylactic is contraindicated 

 in those persons who harbor diphtheria bacilli for fear of producing the 

 disease during temporary depression of the defensive mechanism has 

 been finally dissipated as the result of practical experience. Not one 

 of the numerous bacillus-carriers that have been injected with T.-A. 

 have sickened with diphtheria. Whether or not the active immuniza- 

 tion with T.-A. will help them to get rid of the bacilli is still an open 

 question. 



The subcutaneous injection is recommended as the best method of 

 administration. There can be no doubt that, in many cases, a single 

 injection produces sufficient protection. Such persons are, as a rule, 

 those who have already been sensitized by diphtheria bacilli. For the 

 ordinary run of cases at least three injections should be given. The first 

 injection then plays the part of a sensitizer. Experience shows that 

 sensitization occurs after from ten to fourteen days, which makes it 

 necessary that the second injection should not be given until after an 

 interval of not less than ten days. 



In this country the subject has been studied by William H. Park and 

 his associates, 1 who found that this form of active immunization gave 

 rise to decided antitoxin production in 22 per cent, of susceptible per- 

 sons. The interval between vaccination and the development of im- 

 munity was generally long as a rule, not less than two weeks. Under 

 conditions of exposure about 20 per cent, of those who failed to respond 

 were found to develop clinical diphtheria. Only those persons yielding 

 positive Schick reactions require immunization when exposed to diphtheria 

 and in immediate danger. Antitoxin alone may be used or, if a longer 

 protection is desired and time permits, the T.-A. mixtures may be em- 

 ployed. 



The remedy has not been used sufficiently often to enable us to ex- 

 press an opinion as to its value. Behring believes that its proper use 

 may thoroughly eradicate diphtheria. Obviously, its preparation must 

 be very carefully controlled, and for the present it should be used only 

 in institutions where thorough studies of the blood of patients may be 

 made before and after immunization. 



1 Jour. Amer. Med. Assoc., 1914, 63, 859; ibid., 1915, 65, 2216. 



