[matthewmacleod]

No, it is not true.

There's no ambiguity or uncertainty here – the statement is just factually not correct. A vaccine does not need to "prevent infection", and stating that it does is wrong.

It's particularly galling when this kind of statement is made in a way that says or contributes nothing except a literal falsehood.

[prohobo]

I've been reading the definitions of vaccine, and now I'm confused because it seems to technically have the same meaning as prophylactic - if not, then what's the difference between the two?

[xboxnolifes]

I believe vaccines are a subset of prophylactics. For example, masks, condoms, etc would also be prophylactics.

[prohobo]

So, what happened was that in 2018 they changed the definition of vaccine from "innoculated bacterium/viral agent" to "any substance" (probably to make space for mRNA vaccines), and then changed the result from "that prevents disease" to "that generates antibodies".

Legally, a prophylactic seems to be the same as a vaccine, at least according to this definition from 2013: https://www.law.cornell.edu/definitions/uscode.php?width=840...