A tweet with an image containing words from the Centers for Disease Control and Prevention (CDC) website has gone viral over the last few days, leading to claims the CDC changed its definition of vaccination because the COVID-19 vaccines are ineffective.
The image, shared by US Representative Thomas Massie, a Kentucky Republican, shows three definitions of vaccination listed by the CDC over the years: one from before 2015, then a change in 2015, and finally an update in 2021.
Massie first posted the image in September 2021, tweeting: Check out @CDCgov’s evolving definition of “vaccination.” They’ve been busy at the Ministry of Truth." Posting again in early February, he stated that he "made the graphic, based on definitions from the CDC website, using wayback machine to find copies of their old websites" to highlight the change in definition.
The updated definitions attributed to the CDC are as stated; definitions are updated as and when appropriate, just as Merriam-Webster updated its definition of vaccination in December. However, it's incorrect to imply, as some have, that the definition of vaccination has been changed because of the ineffectiveness of COVID-19 vaccines (spoiler alert: they are extremely effective, particularly against severe illness and death).
The CDC previously defined vaccination as: “The act of introducing a vaccine into the body to produce immunity to a specific disease.” Now, as per the update in September 2021, it defines it as: “The act of introducing a vaccine into the body to produce protection to a specific disease.”
A CDC spokesperson told USA Today back in September, when questions were first raised, that the tweaked definition was clearer and transparent. “While there have been slight changes in wording over time to the definition of ‘vaccine’ on CDC’s website, those haven’t impacted the overall definition,” the statement read. "The previous definition could be interpreted to mean that vaccines were 100% effective, which has never been the case for any vaccine."