Pneumonia in Old Age

EVER since the discovery of the causative agent of pneumonia, its high toll of death has stimulated studies on active immunization against this disease. The experiments, however, when done on human beings were always of short terms. It seemed, therefore, that there was a need for a long term experiment on active immunization against pneumonia. The year by year fluctuations in the incidence and mortality rates might have distorted the results of even the most carefully controlled immunization studies if carried on only for a short period. The perusal of the literature proves that this is exactly what happened; all these experiments, whether done on a large or small scale with vaccines or pneumococcus polysaccharides, were conducted only for one or two years. This is one of the reasons why they contain such contradictory results, contradictory sometimes even within the scope of the same experiment. Furthermore, it seemed evident from