I was surprised that a smallpox vaccine would be required to travel to the US from the UK. Although it was still a threat elsewhere, hadn't smallpox been eliminated from both countries by the 1970s? And wouldn't anyone born in either country have already received a vaccine?
sorry for the delay in the reply,just noticed your post.
I am British and went to Canada in 1971,I was 11.
I recall that there were several vaccines we were meant to have received.I don't recall which ones exactly but I am fairly sure smallpox and diptheria were in there?
The reason I remember it was because the border official got really upset when my mother could not provide written proof that I had received the required injections but she bluffed and said of course I had had them all at school,which was probably true but she just making it up as she went along.
So if we assume,for obvious reasons (common border,few border controls)that Canada and the USA had similar requirements re injections then we can say yes there were still issues over vaccines.
Some people refuse vaccines for various reasons so that is why they ask for proof?