005 - Failure of vaccine

Vaccination in the 19th century, via inoculation of the arm with some infective material (lymph) from an animal or previous patient, was apparently not always reliable in its effectiveness at protecting one from smallpox. This quote from the introduction of this article seems especially relevant in light of the purpose of this blog:

"The frequent failure of vaccination is now so generally admitted, that statistical proofs are not requisite in order to establish its truth. People look upon it as an equal chance, whether those who have been vaccinated shall be able to resist an attack of the small-pox or not, should they be exposed to it; while some go so far as to surmise, hastily and rashly enough, that vaccination is all but useless....a few, still more inconsiderate, boldly declare themselves in favour of the small-pox itself, as the only and surest guarantee of their safety."

On the other hand, supposedly it was readily apparent to medical men of the time that vaccination had reduced the severity of smallpox outbreaks, despite their unreliability in individual cases. This seems believable.

The author lists a number of hypotheses about why a vaccination might fail to protect, especially faults of the vaccinator such as using lymph from imperfect pocks, inoculating with poor technique, and using lymph from pocks that are too old or too young. He puts particular emphasis on the importance of the appearance and character of the pock from which lymph was taken.

Did these aspects really make much difference? I'm dubious; it seems like as long as some form of vaccine infection was achieved, it should be protective. It doesn't seem like the medical men of the time performed any kind of trials; they just went by their own experiences, a series of anecdotes. I could be wrong, though, and it's not that important now anyway.

Citation: Hingeston, J. A. Failure of vaccine. Assoc Med J 1, 412–414 (1853).