_To Dr. Edward Jenner_ _Monticello, May 14, 1806_ SIR, -- I have received a copy of the evidence at large respecting the discovery of the vaccine inoculation which you have been pleased to send me, and for which I return you my thanks. Having been among the early converts, in this part of the globe, to its efficiency, I took an early part in recommending it to my countrymen. I avail myself of this occasion of rendering you a portion of the tribute of gratitude due to you from the whole human family. Medicine has never before produced any single improvement of such utility. Harvey's discovery of the circulation of the blood was a beautiful addition to our knowledge of the animal economy, but on a review of the practice of medicine before and since that epoch, I do not see any great amelioration which has been derived from that discovery. You have erased from the calendar of human afflictions one of its greatest. Yours is the comfortable reflection that mankind can never forget that you have lived. Future nations will know by history only that the loathsome small-pox has existed and by you has been extirpated. Accept my fervent wishes for your health and happiness and assurances of the greatest respect and consideration.
Despite these successes, all was not smooth sailing for vaccination. There were many who doubted the unique ability of cowpox to prevent smallpox and opposed its practice, suggesting, rather, that the treatment was no more than a variation of variolation. This idea was fortified by events occurring in the Smallpox and Inoculation Hospitals in London, an institution initially dedicated to variolation, that now began to practice vaccination under the direction of Drs. Woodville and Pearson. Patients treated with cowpox vaccines would develop numerous pustules, more like smallpox sores, and quite unlike the single inoculation pustule that Jenner reported. Such pustules, we now believe, were due to contamination of the vaccines with smallpox virus that infested the smallpox institution. A brisk debate between Woodville on one side and Jenner on the other caused some in the medical profession to question Jenner's discovery.
Contributing to this questioning of the effectiveness of vaccination was the apparent use by some practitioners of exudates from unrelated infections of a cow's udder that they assumed were cowpox (called by Jenner Spurious Cowpox). Operators using such exudates would report failureto protect against smallpox which they then attributed to failure of cowpox itself. Even when the source of the vaccine was from true cowpox exudates, some reported failures could be attributed to degradation of the vaccine through improper storage and bacterial decomposition.
Finally there were occasional reports of individuals who had earlier been infected with cowpox who years later developed smallpox, reports directly contradictory to Jenner's hypothesis of permanent immunity. Not known at that time by Jenner or his supporters is that vaccination against smallpox is not permanent but must be reinforced every 5 to 10 years. In addition, because of the existence of spurious cowpox, some who believed that they had been infected by cowpox might not have been.
In an effort to clarify several of these issues, Jenner published in 1801 the fourth of this pamphlets on smallpox vaccination: "The Origin of the Vaccine Inoculation". This pamphlet is reproduced here."
In the eighteenth century, before Jenner, smallpox was a killer disease, as widespread as cancer or heart disease in the twentieth century but with the difference that the majority of its victims were infants and young children. In 1980, as a result of Jenner's discovery, the World Health Assembly officially declared "the world and its peoples" free from endemic smallpox."