THE PRACTICAL ASPECTS of immunization have changed in the last few years, and are inevitably destined to change continuously. Not only does modern science keep producing newer and more potent vaccines, but the vaccines themselves alter the distribution of disease agents and thereby the epidemiologic pattern of disease. As Batson and Christie have expressed it: "Immunization procedure is a dynamic subject in need of constant evaluation."
DIPHTHERIA
Nowhere does this phenomenon seem more clearcut than in the case of diphtheria. Whereas 25 years ago a basic course of immunization against diphtheria was essential, repeated natural exposure could be relied upon to boost that immunity throughout later childhood and adolescence. Nowadays the disease itself has become so relatively uncommon in many areas that we need to be reminded by articles like that of Doege, Heath, and Sherman in a recent issue of Pediatrics that 900 cases of diphtheria do occur annually in the United States, and that these cases tend to be grouped in states where immunization programs lag. Because of the very scarcity, in most places, of opportunity for natural exposure, there is an appreciable number of adolescents and adults who, even though immunized in childhood, has again become fully susceptible to infection with Corynebacterium diphtheriae. This falling off of immunity with increasing age must account for small outbreaks of diphtheria among older people in institutions, and for cases in recent years among certain "skid row" groups. It is the reason behind the long schedule of diphtheria toxoid inoculations recommended in the so-called Red Book of the Academy of Pediatrics.
Effects of TMEM154 haplotypes 1 and 3 on susceptibility to ovine progressive pneumonia virus following natural exposure in sheep1,2,3
