The study of disease in municipalities or in places where large collections of statistics are available, gives one the advantage of being able to establish principles. Distinctive features of disease, however, are best elucidated if viewed in a sparsely settled region.
ADVANTAGES OF VACCINATION
Therefore, I have been led to a personal study of small-pox and vaccination such as will warrant the following conclusions:1. Successful vaccination prevented the contraction of small-pox.2. One successful vaccination in children of school age prevented the spread of small-pox to numerous homes.3. A vaccination after exposure and prior to the completion of the incubation period was unsuccessful in preventing the disease or lessening its severity.4. As exposure is possible at any age and under almost any condition and as the effect of vaccination after exposure is uncertain, the most rational course is vaccinal ion at stated intervals, such as infancy, school
KNIGHT HW. VARIOLA AND VACCINATION. JAMA. 1911;LVII(6):478-480. doi:10.1001/jama.1911.04260080042013