"The U.S. was settled, in large part, by working indentured children... Over 1/2 the people who settled the Colonies south of New England came to America under contracts of indenture... The average age of an indentured servant was 14."
~Barbara Woodhouse, "Hidden in Plain Sight"
Because the relationship was seen as that of property.
"The vaccine itself was carried beneath the skin of 22 orphan boys, ages three to nine. During the long crossing, the boys who had not previously contracted smallpox or cowpox were [intentionally, serially infected to keep the vaccine viable]."
Yes, and smallpox was endemic to Europe and Britian, so outbreaks rose up every 10-20 years. This means that any adult alive survived a previous outbreak and were already immune to cow pox and small pox leaving only children or very old as possible hosts for cow pox. (1/2).
No, as far as I understand, this was the case in Britain and parts of Europe and not uniformly. My reply turned into a 7 part thread so let me know if you want to read that. I don't want to just dump it like a reply guy.