On this day, 6 July 1885: Pasteur first uses the rabies vaccine on a human

On 6 July 1885, in Paris, the chemist and microbiologist Louis Pasteur took one of the boldest gambles in the history of medicine. He agreed to treat a nine-year-old boy named Joseph Meister, who had been badly bitten by a dog believed to be rabid, with an experimental vaccine that had never before been used to save a human life.

Rabies was, at the time, an almost invariably fatal disease. Once symptoms appeared, death was virtually certain and often agonising, and the terror it inspired was out of all proportion to the number of cases. A bite from a rabid animal was widely understood as a delayed death sentence, with nothing that medicine could do to prevent it.

Pasteur had spent years studying the disease and developing a treatment. Working with collaborators, he had produced a series of preparations from the spinal tissue of infected rabbits, dried to weaken the agent responsible. Injected in a sequence of increasing strength, the treatment was designed to build the body's defences faster than the infection could take hold, since rabies advances slowly after a bite.

He had tested the approach on animals, but never on a person. Pasteur was not a physician, and administering an unproven treatment to a child carried enormous risk, both to the boy and to his own reputation. According to the historical accounts, he agonised over the decision before proceeding, aware that a failure could be seen as the reckless act of a scientist experimenting on a patient.

The treatment was carried out over a period of days, with a series of injections. Joseph Meister did not develop rabies. His survival, after a bite that would very likely have been fatal, was taken as dramatic evidence that the vaccine worked, and news of the achievement spread quickly, bringing patients bitten by rabid animals to Pasteur from across France and beyond.

The success carried a significance far beyond a single case. It offered powerful support for the germ theory of disease, the idea that specific microscopic organisms cause specific illnesses, which Pasteur had helped to establish and which was still contested by some in the medical world. A treatment built on that theory had, it appeared, defeated one of the most feared diseases known.

The rabies work also helped inaugurate the modern science of vaccination. The principle of deliberately exposing the body to a weakened form of a disease agent, so it could learn to defend itself, extended a concept reaching back to earlier smallpox inoculation. Pasteur, honouring that lineage, adopted the word vaccine in tribute to the pioneering work against smallpox.

The achievement led directly to the founding of the Pasteur Institute in Paris, established a few years later to continue research into disease and to produce vaccines and treatments. The institute became one of the world's leading centres of microbiology, and a network bearing Pasteur's name spread internationally, extending his influence well beyond his own lifetime.

Historians have since examined the episode more closely, noting the ethical questions raised by treating a child with an untested therapy and the risks Pasteur accepted in doing so. Such reassessments place the moment within the standards of its time while acknowledging its extraordinary consequences, and they underline how much the ethics of medical experimentation have developed since.

Joseph Meister survived to adulthood and, by many accounts, remained connected to the Pasteur Institute in later life. The date of his treatment endures as a landmark, the day an experimental injection turned a death sentence into a survivable one and helped open the age in which humanity learned to prevent disease rather than merely endure it.