Has the definition of "vaccine" changed?

It has certainly expanded. Which is to be expected as new technology is developed.

The current Merriam-Webster definition of "vaccine" is too long to take a screenshot of every detail and example. The screenshot at the top of this post is just the highlights, cropped.

I have a few physical dictionaries, too, so I consulted them as well.

First is the 1994 Merriam Webster's Collegiate Dictionary, Tenth Edition (I think you can click on the pictures to make them bigger):

Next is from the 1979 Webster's New World Dictionary:

And finally, from the 1951 Funk and Wagnalls New Practical Standard Dictionary (sorry it's a little blurry):

One change that seems significant to me is that the newer definition doesn't mention "immunity", but "immune response". That's a fairly big difference.

Immunity, in those dictionaries, newer to older, is defined like this:

But "immune response", which doesn't appear in the older dictionaries, is defined this way:

So, yes, the definition of "vaccine" has been changed in ways that reflect advances in medicine, but also in ways that weaken the usefulness of things that would now be defined as vaccines to the benefit of pharmaceutical companies. 

You are free to draw your own conclusions from this information.

Some people say words don't matter and shouldn't be part of the argument-- but when you use the whole definition rather than the shorthand of using the word, they don't like that, either. I always wonder why.

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