The Trump administration is studying the safety of an ingredient commonly used in vaccines, an additive that contains aluminum. Coming after other recent changes to vaccine policy, many public health experts worry that the administration may now try to remove the ingredient.
"We want no aluminum in the vaccine," President Trump said recently at a White House briefing.
For almost a century, some important vaccines, including shots that protect against diphtheria, tetanus, hepatitis and the flu, have included aluminum salts, compounds that contain small amounts of aluminum. They are used as adjuvants to give the immune system an extra kick necessary to make the shots protective.
"Aluminum is added to some vaccines because it's a very safe, but also effective, stimulant of the immune system," says Dr. Jesse Goodman, a vaccine expert at Georgetown University who used to regulate vaccines at the Food and Drug Administration. "It basically stimulates your cells to make more antibodies and a stronger immune response overall."
But Health and Human Services Secretary Robert F. Kennedy Jr., a longtime vaccine critic, has questioned the safety of aluminum in vaccines for years. And a special working group is now studying the "safety of ingredients that are present in multiple different vaccines," including aluminum, for the Centers for Disease Control and Prevention's influential Advisory Committee on Immunization Practices.
One question the working group is considering is "do either of the two different aluminum adjuvants increase the risk of asthma?" according to a document outlining the group's mandate.
Most public health experts say there's no good evidence that aluminum is unsafe and ample evidence that it poses no real concern. In fact, a large Danish study recently debunked any danger.
"We do not see any evidence that aluminum is a cause of serious illness in childhood," says Anders Hviid, a professor of epidemiology at the Statens Serum Institut in Denmark who led the study involving more than 1.2 million Danish children. "There is no scientific reason to take aluminum out of childhood vaccines. There's no science that supports that it's dangerous."
But some researchers welcome the move.
"I really believe that aluminum in vaccines is inherently bad. Full stop," says Christopher Exley, a longtime critic of aluminum in vaccines who recently retired from Keele University in the U.K. "And so any suggestion that we're going to remove it, I think, is absolutely marvelous, not only for making America healthy again but for making the world healthy again."
In addition to concerns over asthma, Exley thinks aluminum can also increase the risk for other health problems, including autism and attention deficit hyperactivity disorder.
Hviid and others say trying to remove aluminum would cause significant problems for protecting people against serious diseases. Most importantly, the vaccines that contain aluminum would be rendered ineffective.
"To simply remove aluminum — in effect destroying or limiting the effectiveness of vaccines — is incredibly stupid," says Dr. Stanley Plotkin, a leading authority on vaccine science at the University of Pennsylvania.
People are exposed to far more aluminum in the environment than from vaccines, Plotkin notes.
And if federal regulators deem aluminum unsafe as a vaccine ingredient, vaccine makers would have to develop and test alternatives, a process that could take years. Such a move could undermine public trust in existing vaccines.
"And what has happened with measles will happen with other diseases — that is, coming back to this country," Plotkin says. "So, do we want that? Well, apparently some people do."
Federal health officials have not stated that they would pull existing vaccines with aluminum salts from the market, or that they want any diseases to return.
HHS press secretary Emily G. Hilliard declined to respond to specific questions about the safety of aluminum adjuvants or the practicality of removing them, but said in an emailed statement that "ACIP is reviewing the body of science related to aluminum and other possible contaminants in childhood vaccine."
And some scientists are open to at least studying the question of removing aluminum salts.
"It's human nature to try to make things even better, right?" says Dr. Ofer Levy, a pediatrician who runs the Precision Vaccines Program at Boston Children's Hospital. "So with all of the sophisticated science we have in the year 2025, probably there's room for improvement."
But Levy stresses that any changes should only be made if unbiased, well-conducted studies support that. In the meantime, Levy and others say that no one should hesitate about getting a vaccine containing aluminum.
"The question becomes: How do we give voice to legitimate concerns about vaccines without throwing the baby out with the bathwater?" Levy says.
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