CONTRAINDICATIONS TO ACTIVE IMMUNIZATION 667 



and indicates that the vaccine in question possesses some potency. 

 Allen, who has an exceptionally rich experience in vaccine therapy, 

 frequently mentions the desirability of administering doses sufficiently 

 large to evoke slight reactions. 



Following the administration of a vaccine it is believed that the 

 quantity of opsonin in the body-fluids is temporarily decreased, and that 

 the inoculated person is, therefore, more susceptible to infection (nega- 

 tive phase) (Fig. 56). It can readily be understood how a vaccine 

 may temporarily depress the cells and defensive mechanism in general, 

 but just how it may bring about an actual decrease in opsonin it is 

 more difficult to understand, as the actual amount that may be used 

 in dealing with the vaccine itself must be small. Veterinarians are 

 careful not to expose cattle to infection immediately after they are im- 

 munized with anthrax vaccine, on account of this hypersusceptibility 

 to infection. In general, however, I have observed that most im- 

 munizators are prone to regard the question lightly, and to neglect 

 the importance of the negative phase, whereas some deny that it ever 

 exists. 



Contraindications to Active Immunization. It should be emphasized 

 that a properly prepared vaccine is a potent substance capable, when 

 given in excessive dosage or when otherwise injudiciously administered, 

 of doing much harm. A vaccine stimulates body-cells, and unless the 

 cell can withstand the stimulation, the administration of vaccine may 

 do actual harm. This is the main reason why vaccines should be used 

 very cautiously, if at all, in the treatment of severe generalized infections. 

 In passive immunization the conditions are different, as the body-cells 

 are not taxed, but rather, through the neutralization of the toxic sub- 

 stances which they are combating, they are relieved, and an antibody- 

 laden serum may, therefore, be freely administered in severe infections. 



In active immunization for therapeutic purposes the conditions 

 should be carefully weighed and the treatment conducted by one who is 

 qualified to judge of the potencies of harm and good in a vaccine, and 

 who has had sufficient experience to guide him in dosage and frequency 

 of inoculation, the main objects being to tide over and aid nature during 

 an acute infection, and to arouse and stimulate her during a chronic 

 infection. 



In prophylactic immunization the physician should satisfy himself 

 that the patient has no latent or active infection that may be rendered 

 worse during the temporary depression that follows inoculation. It is 

 true that this depression is fleeting and temporary, and that the possi- 

 ble harm incurred may be far outweighed by the ultimate good, but vac- 



