[dionian]

Before 2020, vaccines referred to things like attenuated viruses - you were basically being given a small weakened dose of the actual pathogen to prime your immune system. mRNA shots are a different animal and they are quite new.

[Volundr]

Far be it from me to doubt a stranger on the Internet, but can you point out any medical textbook or dictionary written pre-2020 that limits the definition of "vaccine" to "attenuated viruses"?

[Izkata]

This is the dictionary people were pointing at when it happened:

2021-01-18: https://web.archive.org/web/20210118193104/https://www.merri...

2021-01-26: https://web.archive.org/web/20210126065143/https://www.merri...

[Jedd]

I was sure that pre-2020 - going back 40y or so prior - VLP's were also generally regarded as coming under the umbrella term 'vaccine'.