By 1798, Jenner had succeeded in demonstrating the protective quality of the cowpox virus against smallpox, by putting on record details of 23 cases, contracted either casually or by direct inoculation.
Sixteen of these had occurred accidentally among dairy workers in the course of occupations connected with cows and horses; the rest were done under Jenner’s direction.
Among the persons inoculated was Jenner’s own little second son, Robert Harding Jenner, an infant eleven months old.
Jenner demonstrated conclusively that the cowpox protects the human constitution from the infection of smallpox.
After Dr. Jenner had made his tests, he prepared a pamphlet for publication.
He also went to London, so that he might have the opportunity to introduce the subject personally to friends and demonstrate the truth of his assertion to them.
He remained in London for nearly three months without being able to find anyone who would submit to vaccination.
Jenner went back to Gloucestershire, disappointed.
It happened, however, that soon after his return home, a distinguished London surgeon named Cline resolved to make a trial of the vaccine material which Jenner had left with his friends.
The patient was a child suffering from a form of chronic hip-joint disease.
The vaccine material was inoculated, and the vaccine vehicle ran rather a normal course and healed fully.
The little patient was afterward inoculated with smallpox virus and found to be incapable of acquiring that disease.
This case attracted considerable attention.
The child was in a run-down condition, and the vaccine material might very well have provoked a rather serious local reaction.
In a way, the fate of vaccination hung in the balance and good luck was in its favour.
Mr. Cline, however, after this, became a strong advocate of vaccination, and brought it very decidedly before the London physicians.
It was not long before the opposition to the practise of vaccination took definite form.
One of the best-known London physicians of the time, Dr. Ingenhouz, became the leader of a strong faction of the medical profession of London, who not only would have nothing to do with vaccination, but proclaimed openly that it was a dangerous innovation, absolutely unjustifiable, and communicated a disease without protecting against any other.
Dr. Watt from Glasgow blamed the vaccine for the increase in severe cases of measles and measles-related deaths among children.
Fortunately, only a few colleagues were so illogical, and an excellent idea of how much Jenner’s discovery was appreciated by his contemporaries may be obtained from the number of honours, diplomas, addresses and communications from public bodies and distinguished individuals which he received.
Most of the prominent medical and scientific societies of Europe elected him a member or sent him some special token of recognition.