Is there a specific year that marks the official acceptance of the germ theory? In the references, it is always quoted the work of Pasteur, Koch, and Lister, but their work is spread over decades and does not mean that their papers were accepted by the medical community.
Is there a watershed year instead? Perhaps a peculiar conference where the doctors wrote black on white that the new theory had become the new paradigm? Or a paper that encountered the agreement of all the peers?
It was only after Darwin's 1859 theory of evolution sparked an interest in chemical evolution as an explanation for life that the germ theory was accepted. ref As a comparison theory, it took until the 1950's for a majority of scientist to agree that evolution was caused only by natural selection, a 90 year gap until consensus.
Pasteur published his germ theory in 1861. It took about twenty years for the most eminent international scientists (i.e. Tyndall) to give conferences on it in the UK and for Koch to evidence it in Germany. From the 1880s, Germ Theory was hugely influential, affecting nearly every aspect of medicine including public health, surgery, hospitals, training and treatments. In the 1950's we can find books like i.e. "Pasteur, plagiarist, imposter: The Germ Theory Exploded"
In France, Louis Pasteur was elected a free associate of the French academy of medicine in 1873, won the Copley medal of the Royal Society of London in 1874, medal of Grand-Officier de la Légion d'Honneur in 1878, and designed a vaccine for sheep in 1881.
Following France, Germany was one of the first to officially recognize germ theory:
On 24 March 1882 at the Berlin Institute for Physiology, Koch announced the discovery of the tuberculosis pathogen – with his lecture on the “Aetiology of Tuberculosis” he became world famous overnight. In the course of the 19th century, Roughly a seventh of the population of the German Reich died of the disease. Now Koch demonstrated that tuberculosis was triggered by the tubercle bacillus.
In 1885, Friedrich-Wilhelms-University in Berlin founded the Hygiene Institute, which was managed by Robert Koch.
In 1891, Koch agreed to direct the newly-founded Royal Prussian Institute for Infectious Diseases. ref
He was awarded the Nobel Prize in Medicine in 1905.
A famous epidemiologist, William Farr, working on cholera, published "a monograph" which showed that mortality was extremely high for people who drew their water from the Old Ford Reservoir in East London. Farr's work was then considered conclusive... Physicians were publicly denouncing germ theory in major newspapers 20 years later:
Irish physicist and science popularizer John Tyndall was superintendent at the Royal Institution in London and had published scientific works on heat, light and sound, as well as popular books. His ideas on germs became controversial in January 1870 after giving a lecture to the Royal Institution entitled Dust and disease. Here, he first reported experiments demonstrating that dust was mainly composed of organic matter, something he had not anticipated. He then demonstrated, using his light scattering assay, that air filtered by cotton wool was ‘optically empty’, meaning that the path of the beam appeared black, which he also saw with air that had been left to settle for long periods of time in a sealed glass chamber. Finally, he reported that his own breath, especially the end of his expiration, was remarkably free of floating matter. He had recently been taken by Lister’s methods for antiseptic surgery, which argued that infection spreads through the air due to the microbes contained within it and viewed his data as entirely consistent with these. Hence, Tyndall extrapolated his conclusions to make a strong statement in favor of the germ theory of disease; an idea which had not yet found acceptance with the majority of the English medical profession. Following Tyndall’s 1870 lecture, there was much criticism of his conclusions from prominent physicians who believed that ideas relating to the nature of disease ‘pertain most to the biologist and the physician’ and that a physicist should know better the facts of epidemic disease before delving into the living world. The pathologist Charlton Bastian confronted Tyndall directly in a series of letters to The Times, playing down the evidence supporting germ theory and discussing his own experiments which disagreed with previous work by Pasteur, Lister and the like. Bastian then published a 1,115-page book in 1872 describing many experiments that he argued proved that microbial growth could occur in conditions in which Pasteur argued...ref
