96 VACCINE AND SERUM THERAPY. 



clinical evidence as is usually found in infections caused by the 

 corresponding organisms, or if the patient has been exposed to 

 infection from a previously diagnosed case of the communicable 

 disease. 



When injections of immune sera are to be made frequently, 

 and over long periods of time, as is the case with most anti-bac- 

 terial sera, the injections should be made at intervals of less than 

 ten days, because, if the interval is longer than this, serum disease 

 is more likely to develop. 



The indications for injection of immunizing doses are not 

 clear nor definite. Nurses and doctors, however, now rarely re- 

 ceive immunizing doses of immune serum. This is especially 

 true of diphtheria anti-toxin. The reasons for the abandonment 

 of the practice of immunizing doctors and nurses, are based on 

 the fact that doctors and nurses are better able to avoid infec- 

 tion and so usually do not contract the diseases of their patients, 

 and because the protection conferred by passive immunization 

 is only of short duration. Doctors and nurses, because so 

 frequently exposed to infectious diseases, would have to be 

 injected frequently and at different intervals of time to be 

 immune to the various infections of their patients. Serum 

 injections at intervals of more than ten days, however, are more 

 likely to give rise to serum disease. 



The custom concerning immunization of individuals against 

 possible infection because of exposure, varies. It is the rule of 

 some physicians, upon the diagnosis of diphtheria in one member 

 of the family, to give all members of the family an immunizing 

 dose of diphtheria anti-toxin. In some of the large children's 

 hospitals and clinics diphtheria anti-toxin is given to all patients 

 on admission, this being done to avoid the outbreak of diph- 

 theria epidemics. Such preventative measures hardly seem 

 warranted. The custom of most physicians now is to give im- 

 munizing doses of some specific ant i -sera to such members of a 

 family or household as are most likely to contract the disease; 

 thus for example, diphtheria anti-toxin is given only to the 

 children in a home in which there is diphtheria. On this basis 

 administration of anti-sera is justifiable, while indiscriminate 

 immunization by the injection of serum is costly and may 

 also sensitize individuals to serum, which might later make the 



