Merriam Webster's old definition did not exclude therapeutic vaccines. But it did exclude vaccines prepared from viruses.[1] Probably you heard about diphtheri

Merriam Webster's old definition did not exclude therapeutic vaccines. But it did exclude vaccines prepared from viruses.[1] Probably you heard about diphtheria and tetanus vaccines before 2020. They are prepared from toxins. Other definitions did not restrict what a vaccine must contain.[2] [1] http://web.archive.org/web/20190118214500/https://www.merriam-webster.com/dictionary/virus http://web.archive.org/web/20190118214500/https://www.merria... [2] https://web.archive.org/web/20160402152957/https://www.dictionary.com/browse/vaccine https://web.archive.org/web/20160402152957/https://www.dicti...