Why are they re-defining all the key terms related to this "health emergency??"

Pandemic

Vaccine (it's really gene therapy)

Herd immunity

When words don't meet the meaning the left needs, they change 'em to deceive people and cover their own buts. If a gene therapy treatment can be called a vaccine, it eliminates all risk for the Pharma company.

https://articles.mercola.com/sites/articles/archive/2021/03/22/who-pandemic-definition.aspx