Florence Nightengale pioneered more rigourous statistical data in mid 1800s. Still from then it was a long time before technology to allow better record keeping came about. It was just not possible to take and share records of health from even near every person in the world. So the number of deaths recorded pre-vaccine era is stronger evidence considering that. When was Autism even labelled and 'discovered', btw? Anti-vaxxers are probably descendants of ppl who thought every aberrant behaviour was a demonic possesson.

Florence N:
http://thisisstatistics.org/florence-nightingale-the-lady-with-the-data/