Vaccines are sufficiently easy to make that people in the 19th century could make them. The hard part isn't making a vaccine, it's making one that's safe and r

Vaccines are sufficiently easy to make that people in the 19th century could make them. The hard part isn't making a vaccine, it's making one that's safe and reliably effective. Using 19th century techniques will kill you an unacceptably high proportion of the time (well, unacceptable unless it's something like widespread smallpox or, debateably, covid) and also often won't work.