AN ATTEMPT TO INTERPRET PRESENT-DAY USES OF VACCINES
Authors: THEOBALD SMITH
Journal: JAMA (1913)

The artificial production of immunity toward infec- tious diseases by the use of modified viruses has been one of the major problems of medical science for a generation.The antecedents which have led up to such an intensive cultivation of this subject are relatively few and simple.Persons who successfully passed through an attack of such a characteristic disease as small-pox were thereafter able to mingle with the diseased, nurse them, and remain well.Persons who had been inoculated with the products of this affection developed a relatively mild type of small-pox, and were thereby protected from the more severe spontaneous attack.Owners of domestic animals had also, at times, resorted to such inoculations to hurry along an animal plague, by inducing a somewhat less severe attack.These facts are said to have been known to the Chinese thousands of years ago.In the last years of the eighteenth century Jenner made known his discovery that cowpox inoculated into man protected him against small-pox.The scientific imagination of l'astenr, carrying these simple data into the domain of experimental biology, evolved new met hods for inducing immunity, not only before but also after natural infection had taken place, by subjecting the respective viruses to various modifying processes, since Pasteur's time the attempts ¡it modify-LUg viruses In make them as harmless as possible, while retaining their efficacy ¡is immunizing agencies, has been Steadily going on.Moreover, their use is no longer limited to the prevention of infection, but it has been °0ldly carried to the heart of disease itself.There is scarcely an infection, however active in its manifesta¬ ron, which is not ¡tl present attacked with vaccines.' fojjerly to evaluate this present-day movement in ""'dicine in the time al my disposal, even in its gross '."''lines, is impossible.I can only indicate a Pew '"ndiiiuental.well-established fuels in experimental "" diiline ¡nul suggesl a few hypotheses which we may use as lanterns to penetrate here and there the dense gloom which still hovers over immunity in some of ils manifestations.Perhaps the most importan!aid we can gel is from a slll|I.Y of the natural history of infectious diseases; in "'her words, from an inquiry bato what Nature herself '"'"'nplishcs with one attack of a given disease.In this S,'"I.V we shall lind it convenient to group together infecí ions among the members of which a certain degree of similarity exists, and within which the production of immunity requires approximately the same expenditure of energy.Thus, the eruptive diseases are in a class by themselves.They run their course with relative rapidity and the system rids itself of the infecting agent completely.They appear to be of all diseases the most, readily amenable to vaccinât ion.There is a great gap between these affections and such diseases as leprosy on the one hand, and miliaria on the other.In the former the disease may last ¡t lifetime, and il would be difficult to determine just what degree of immunity is gained by the leper.Malaria may eventually subside, bul the inl'ecting agent may persist indefinitely, l'util recently it was quite generally denied that any immunity could be acquired toward the malaria] parasite.The same doubts have been maintained toward the acquisition oí immunity in tuberculosis.Recently, P. II.Römer1 lias shown that guinea-pigs made tuberculous by minute doses of virus become immune to subsequent infection with minute doses.applied to the skin, which cause a progressive disease in control animals.The tuberculous guinea-pig, accord¬ ing to his further researches, becomes immune to the feeding and the inhalation of tubercle bacilli, and to contact infection in cages with guinea-pigs having tuber¬ culous ulcers.The study of protozoan parasites causing