On August 26, 2021, this was the definition used by the CDC to describe what a ‘vaccine’ is:
Link here: http://web.archive.org/web/20210826113846/https:/www.cdc.gov/vaccines/vac-gen/imz-basics.htm
They have used this definition in their site since May 16, 2018.
On September 1, 2021, they suddenly changed that definition into the following:
Link here: https://www.cdc.gov/vaccines/vac-gen/imz-basics.htm
We can only stipulate on the reasons for this change but there is clearly a correlation between this change and the fact that the COVID 19 vaccine does not provide full immunity to the virus, and that countries with high vaccination rates like Singapore and Israel continue to experience surges in cases.
References
Centers for Disease Control and Prevention. (2021, September 1). Immunization Basics. https://www.cdc.gov/vaccines/vac-gen/imz-basics.htm