U.S. Health and Human Services Secretary Robert F. Kennedy Jr. announced what may be one of the most important health policy decisions in decades: a full federal ban on the use of mercury-based preservative thimerosal in vaccines.

Health Secretary Robert F. Kennedy Jr. issued a sweeping executive order on July?23, 2025, mandating vaccine manufacturers to eliminate the mercury?based preservative thimerosal from all influenza vaccine formulations sold in the United States.

Kennedy justified the move by citing long-held claims that prenatal exposure to even tiny doses of ethyl­mercury in multi?dose vials can lead to "mild to severe mental retardation" in unborn children.

According to The Conversation:

RFK Jr. has long linked thimerosal to autism – a connection that extensive scientific research has thoroughly debunked.

Thimerosal is an organic chemical containing mercury, used as a preservative in vaccines since the 1930s. Its effect comes from the mercury that disrupts the function of enzymes in microbes, such as bacteria and fungi. This prevents contamination of vaccines while they are stored in vials. Mercury, however, is also well-known as a potent toxin acting on cells the brain.

Much of mercury's toxicity to brain cells stems from the same attributes that make thimerosal such a useful preservative. It disrupts the basic biological function of cells by changing the structure of proteins and enzymes.

In the brain, this can lead neurons to become excessively active, can impair the way they use energy, it can increase inflammation and lead to the death of neurons. While mercury poisoning can damage brain function in adults, babies are even more vulnerable.

Kennedy revealed that flu shots laced with this toxic compound were still being administered to pregnant women and children up until last week.