It was informative still- I was surprised that the average lifespan was only 45. It does make some sense I suppose: penicillin was still thirty years away and there wasn't a single vaccine yet.
The vaccine had been invented more than 100 years prior to 1900. I'm not sure how wide-spread they were at that point, but the vaccine was invented some time in the 18th century. Antibiotics -- you're right, not discovered yet in 1900.
I stand corrected. Wikipedia lists some interesting proto-vaccines in the 1800s and earlier (including one for smallpox). There was a major increase in the availability and breadth of vaccines in the 1900s, but a lot of groundwork was already laid before that. Thanks for the correction.
Anyway, I'd delete my original comment, but evidently too much time has elapsed.
Serves me right for writing "Clearly" :)...Hopefully at least the life expectancy link in it was informative.