NB/ Germ theory led to a number of important breakthroughs in vaccinations in the 19th century - perhaps most importantly Pasteur was able to prove how the technique of vaccination worked and Koch was able to establish a progress of isolating individual bacteria enabling vaccination to take off.
However as the timeline below shows most progress was made in the twentieth century.
18th century 1798 First vaccine for smallpox, first vaccine for any disease developed by Edward Jenner.