As the public learns more about the virus that caused the COVID-19 pandemic, health agencies have continually updated their guidelines to align with scientific breakthroughs. This includes the Centers for Disease Control and Prevention (CDC), which was reported to have changed its definition of vaccine.

Was There a Change in CDC Definition of Vaccine?

In September 2021, a video circulated on social media stating that the CDC had changed its definition of a vaccine, triggering various responses from the public. A comparison of the archived CDC web page from May 2018 and its current web page confirms that the definition was indeed changed.

Before September 1, 2021, the CDC defined the vaccine as "a product that stimulates a person's immune system to produce immunity to a specific disease, protecting the person from that disease." The agency states that a vaccine is merely "a preparation that is used to stimulate the body's immune response against diseases."

Meanwhile, vaccination was previously defined as "the act of introducing a vaccine into the body to produce immunity to a specific disease." The CDC's current definition is "the act of introducing a vaccine into the body to produce protection from a specific disease."

There were speculations from the public that the unannounced changes were the attempt of the CDC to hide the fact that COVID-19 vaccines are not 100% effective at preventing viral infection. Others also believe this change was motivated by the increase in infections in the COVID-19 vaccinated population during that year.

However, a CDC spokesperson clarified that while there have been slight changes in wording on the agency's website in defining a vaccine, those have not affected the overall definition. Aside from this, the previous definition could also give misleading information that vaccines were 100% effective, which has not been the case for any shots, so the current definition was made to offer transparency.

It is also not the first time the CDC has changed its definitions of certain terms on its website. A few months before the definition of "vaccine" was changed, the agency also reworded the meaning of "close contact" when about the transmission of COVID-19.

READ ALSO: Did CDC Intentionally Delay Release of Information on COVID-19 Animal-to-Human Transmission?


How Will It Affect Public Health?

In February 2022, U.S. Representative Thomas Massie amplified the allegations that the changes in definition are due to the ineffectiveness of the COVID-19 vaccine. The Kentucky Republican has been known for being critical of pandemic masks and vaccine guidelines.

Dr. John P. Moore, a microbiology and immunology professor at the Weill Cornell School of Medicine, said Massie's comments reflected disinformation based on semantics, not science.

Moore explained that he has no problem with the changes made by the CDC since they are informative and not sinister. He further explained that the vaccines are meant to protect a person against disease, not against infections.

Meanwhile, Dr. Ryan Langlois, a professor of microbiology and immunology at the University of Minnesota, noted that the agency's changes make total sense and even add nuance, considering emerging developments in making vaccines, such as mRNA technology.

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