VACCINE THERAPY. This consists in the introduction into the body of a suitable vaccine, in order to stimulate the tissue cells to elaborate a sufficiency of specific antibodies to resist the subsequent invasion of a particular micro-organism ; or in the case of an already infected individual to prevent the further multi plication and diffusion of the invading bacterium—in other words, to establish a condition of active immunity.
To Edward Jenner belongs the credit of exploiting the use of an attenuated virus for the production of an active immunity to smallpox, and originally the term "vaccine" was restricted to the virus of smallpox as altered by its passage through the bovine species, in which it gives rise to cow-pox or vaccinia. Pasteur then applied the principle to the prophylaxis of bacterial infections and Sir Almroth Wright expanded it to embrace not only the preven tion but'also the treatment of microbial disease. Consequently, the word "vaccine" now includes suspensions of bacterial cells and emulsions of bacterial protoplasm, which when introduced into the human economy result in the formation of specific antibodies.
In either case the plan adopted was to inject successive quanti ties of bacterial protoplasm derived from artificial cultures of the particular micro-organism under study. In the initial stages of the process these cultures are usually modified by some physical agent, such as heat, in order to attenuate or destroy the virulence of the microbe. For instance, Pasteur vaccinated sheep with cultures of the anthrax bacillus which had been attenuated by growth at a temperature (4r° C) some degrees above the optimum, to protect them against the natural disease splenic fever; and Wright used cultures of B. typhosus, killed by heating to 60° C for the protection of British soldiers in India against typhoid fever.
The success that attended this work of Wright, sufficiently notable in the later stages of the Boer War, reached its culmination during the World War, when first typhoid, and subsequently paratyphoid, fevers were eliminated from the British Army by the use of appropriate vaccines, and in consequence prophylactic vaccination against these diseases has established its position in preventive medicine.
Attempts have naturally been made in the direction of prophy laxis against many other infective diseases by the use of special vaccines, as, for example, cholera ; plague ; dysentery ; cerebro spinal fever; tuberculosis; pneumonia; influenza and the common "cold"; but although considerable success has been attained, the results have not presented the uniformity of those achieved in the prevention of typhoid and paratyphoid fever. At the same time,
it must be conceded that it is a difficult matter to arrange "mass" experiments in which the numbers of inoculated and uninoculated or "control" individuals are sufficiently large to permit of the appli cation of statistical methods in the evaluation of the results obtained, particularly in view of the very brief "incubation" period of many of these diseases. This difficulty becomes even greater when vaccines are employed in the treatment of individuals already incapacitated by bacterial infections, for here each case must be judged as a separate entity and accessory means of treat ment, to say nothing of the long arm of coincidence, are factors which cannot be ignored when attempting to form a just estimate of the value of vaccine therapy. In the opinion, however, of those who have devoted themselves to the study and application of this type of medication no reasonable doubt exists as to the importance of what may be termed specific therapy.