Infectious Diseases
Although their cause was uncertain until the last third of the nineteenth century, childhood exanthemata and whooping cough were recognized by a majority of physicians as contagious.
The responsible agent was thought to be a specific virus, or morbid poison, often undetectable by the senses. However, physicians who subscribed wholeheartedly to the mi- asmic theory of transmission did not accept the notion of a causal virus or physicochemical agent of infection. Instead, they believed that polluted air, or miasma, could excite a variety of fevers, the specific nature of any epidemic being determined by the geography of the locality, the season of the year, or the personal constitution. For example, William P. Dewees, author of the first U.S. pediatric textbook (1826), doubted that whooping cough, mumps, and measles were contagious. In his view they were epidemic diseases, that is, dependent on some condition of the atmosphere. In his words: “It is a rule, with few or no exceptions, that, where a disease can be traced to atmospherical influence, it does not prove contagious. Nature indeed can hardly employ two such opposite causes to produce the same effect” (Dewees 1829).In 1798 Edward Jenner had advocated the use of cowpox (vaccination) as protection against smallpox, a disease particularly fatal to infants. In a remarkably short time, vaccination replaced inoculation as the means of providing immunity to smallpox (Ed- wardes 1902; Hopkins 1983). However, because the mechanism of protection was not understood, confirmed miasmatists continued until the end of the nineteenth century to protest vaccination, which contradicted their epidemic, nonspecific theory of disease (for antivaccinationist views, see Crookshank 1889; Creighton 1894; Tebb 1898). In their opinion, the decreased incidence of smallpox after mass vaccination was due not to protection afforded by vaccination, but to a natural decline in smallpox epidemics counterbalanced by an increase in other diseases such as measles and whooping cough.
Immunity began to be understood when Louis Pastern" discovered that the injection of an attenuated culture of chicken cholera protected laboratory birds from the effects of a subsequent inoculation of virulent culture (for a discussion of Pasteur’s work on attenuation, see Bulloch 1938).
Strategies of attenuation were enlarged to include dead organisms and prepared extracts; at the same time immunity began to be explained by the production of specific serum antibodies to bacterial antigens and of antitoxins that neutralized toxins. Scientists undertook the preparation of specific protective sera with striking success in 1894, when Pierre P. E. Roux demonstrated the value of diphtheria antitoxin, which had been discovered earlier by Emil von Behring and Shibasaburo Kitasato.Diphtheria antitoxin, although frequently lifesaving, conferred only passive, temporary immunity and could not prevent the spread of disease. Gradually a safe attenuated toxin (toxoid) was developed so that by the 1930s children could be actively immunized against diphtheria. By this time, a vaccine against pertussis had also been discovered, and passive immunization against tetanus, as well as certain types of pneumococci and meningococci, was possible. Research continued apace during the Second World War, when a safe tetanus toxoid was discovered (Dowling 1977). This was followed by the discovery of poliomyelitis vaccine in 1956 and, more recently, of vaccines for rubella, measles, and mumps. Today, a full immunization program during infancy eliminates, in large measure, the ill health, chronic disability, and mortality that were once associated with the common infectious diseases of childhood.