July 17, 2025

Many vaccines contain aluminum, but it does not cause autism, study finds

The findings come as HHS Secretary Robert F. Kennedy Jr. questions the safety of the ingredient, which is used to boost the body's immune response.

By Shamus Clancy
PhillyVoice Staff

Jay Janner/USA TODAY NETWORK via Imagn Images

A Danish study finds no link between aluminum in vaccines and an increased risk of autism, asthma and dozens of other health conditions. The photo above shows the measles, mumps and rubella vaccine, which contains aluminum.

A new, Danish study found no link between aluminum in early childhood vaccines and an increased risk for autism and dozens of other health conditions. The finding refutes claims by Health and Human Service Secretary Robert F. Kennedy Jr. and other vaccine skeptics that the element is an unsafe ingredient.

The study, published in the Annals of Internal Medicine, followed more than 1.2 million children born between 1997 and 2018 for eight years to assess their risk of developing 50 chronic health conditions, including asthma, allergies, autism, attention-deficit/hyperactivity disorder and others.

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The study concluded that "cumulative aluminum exposure from vaccination during the first two years of life was not associated with increased rates of any of the 50 disorders assessed."

Vaccine skeptics have long accused childhood immunizations of causing autism despite studies repeatedly finding no such evidence.

An estimated 2.21% of U.S. adults have autism spectrum disorder, according to the National Institutes of Health. Autism spectrum disorder includes a "broad range of conditions characterized by challenges with social skills, repetitive behaviors, speech and nonverbal communication," according to the Autism Speaks organization.

The Danish study comes as Kennedy has questioned the safety of aluminum salts in childhood vaccines. In 2024, Kennedy claimed the use of aluminum in vaccines is "extremely neurotoxic" while speaking on "The Joe Rogan Experience" podcast.

Last month, Bloomberg News reported that Kennedy is considering asking the Centers for Disease Control and Prevention's vaccine advisory panel to examine shots that contain aluminum. Kennedy previously had fired all 17 members of that panel, which helps set vaccine policies in the U.S. Days later, he named eight new members.

Anders Hviid, the senior study author of the Danish study, told NBC News that his team's research was prompted by a 2022 CDC-funded study that suggested childhood vaccines increase the risk of asthma. That study was widely criticized, because it failed to distinguish between aluminum from vaccines and aluminum from other sources, and included inconsistencies.

Aluminum is the third most abundant metal on Earth and people are commonly exposed to aluminum through breast milk, air and water, Dr. Paul Offit, director of the Vaccine Education Center at the Children's Hospital of Philadelphia, told the outlet. Distinguishing between aluminum from those sources and aluminum from vaccines is imperative.

"If you are looking at people who got vaccines that contained aluminum versus those who had fewer, you have to control for confounding factors, you need to know that the only different source of aluminum these people received was from those vaccines," he said.

Aluminum is used in several vaccines that children receive in their first two years of life, including shots to prevent hepatitis B, meningitis, pneumonia and diphtheria, tetanus and pertussis, according to the Children's Hospital of Philadelphia. It is not used in vaccines that use live, weakened viruses to produce immunity, like the shot that prevents measles, mumps and rubella.

Aluminum is added to some vaccines to boost the body's immune response. The ingredient's inclusion in vaccines has repeatedly has been evaluated as part of clinical trials for decades.

The vaccines infants receive in their first six months of life expose them to about 4.4 milligrams of aluminum; by contrast, one slice of American cheese contains as much as 50 milligrams, the New York Times reported in January.

Hviid told the Times that more research into the effects of aluminum adjuvants is welcome, but he said it may not be enough to change the minds of skeptics concerned about the long-term effects of vaccines, saying "You cannot prove a negative."

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