The word “vaccine” comes from the recognition that people could gain immunity against smallpox via infection with the less-deadly (and live) virus cowpox. http

The word “vaccine” comes from the recognition that people could gain immunity against smallpox via infection with the less-deadly (and live) virus cowpox. https://en.m.wikipedia.org/wiki/Vaccinia https://en.m.wikipedia.org/wiki/Vaccinia The definition has never been constrained to dead pathogens.