() New polling from the Economist and YouGov found that 50% of Americans disapprove of Health Secretary Robert F. Kennedy Jr.’s decisions regarding a key vaccine advisory committee.

The same polling found that a supermajority of Americans, 76%, say vaccines in general are safe.

Kennedy fired the entire vaccine advisory panel at the Centers for Disease Control and Prevention, replacing the 17 members with eight new ones, some of whom have a track record of vaccine skepticism.

The panel is set to meet next week, and one item on the agenda is reviewing the measles, mumps and rubella vaccine in children under 5 years old. The panel is also set to reexamine several other issues that scientists and public health experts have considered settled for decades.

The panel is specifically taking a look at two ingredients: aluminum additives used in most childhood vaccines and thimerosal, a mercury-based preservative still used in some flu shots.

The review could impact vaccines for polio, hepatitis A and B, HPV, meningitis and whooping cough. The U.S. has seen increasing numbers of measles cases in recent months, largely driven by unvaccinated people.

Aluminum has been used to boost immune response for nearly a century, and thimerosal was phased out of most childhood shots in 2001 but still appears in multidose flu vials.

Before becoming HHS secretary, Kennedy wrote a book asserting that thimerosal causes autism and should be abolished. That claim has been disproven by health experts, including the agencies Kennedy now leads.

Scientists have debunked claims linking vaccines and autism, and medical experts have said that both aluminum and thimerosal are safe. But Kennedy and his panel have argued they still aren’t sure and that it’s time for a reevaluation.

Critics have said the actions aren’t about safety but are instead an effort to sow distrust in vaccines.

The panel is expected to vote next week on whether to keep thimerosal in flu shots, and a broad review of aluminum could come in July.

Last month, Kennedy changed the CDC’s recommendations for the COVID-19 vaccine without a vote from the panel.