"It's a falsehood that can undermine trust in vaccines and endanger our children," Dr. Tom Frieden, a former CDC director and president of the nonprofit Resolve to Save Lives, said in a press call Febuary 4. Committee members are vetted for conflicts of interest and close ties to vaccine makers. Once they become members, they are required to file disclosure reports yearly and must recuse themselves from discussions and decisions for topics where they have actual or perceived conflicts of interest.
As an advisory committee to the CDC, the panel relies on support from CDC employees.
A CDC official serves as the group's executive secretary, and its public meetings often include presentations prepared and delivered by CDC staff. For instance, the agenda for an upcoming meeting in late February has CDC employees presenting on every topic under consideration.
Typically, these presentations include data collected and analyzed by the CDC, and shares assessments of the benefits, risks and costs of vaccine products, graded to reflect the quality of the science they're basing it on.
But early moves by the new Trump administration to curtail public communications from health agencies, and alter content on the CDC's website to comply with executive orders on gender identity and DEI, have raised the prospect that future public presentations may be filtered through the lens of political appointees.
"I think this is a legitimate concern," says Modlin, the former ACIP chair.
"If there was a statute requiring that some of the information be, for example, scientifically objective, it might be different, but there isn't such a statute. The administration can change the information provided [if it wants to]," Reiss says.
Besides public meetings, ACIP members attend closed, monthly work group meetings focused on topics such as vaccines for Mpox, COVID-19 and HPV alongside staff from the CDC and other agencies and subject matter experts. "If you control the CDC staff, you could control the presentation and the data given to the committees, so that's another area of access," Reiss says.
And since these work groups are "guided by CDC and HHS priorities, and by the perceived need for expert advice to inform development of immunization policy," according to ACIP's standard operating procedures, heads of CDC and HHS have leeway to add different perspectives to existing work groups, or create new ones focused on their interests.
There are limits to ACIP's authority. The immunization committee makes recommendations to CDC and if the CDC director approves them, as is usually the case, they become official CDC policy. "But the CDC director doesn't need necessarily to follow that advice," says Dr. Paul Offit, director of the Vaccine Education Center at the Children's Hospital of Pennsylvania, who served on ACIP from 1998-2003. The director also has the power to reject or amend them.
Trump's pick to lead the CDC, Dr. Dave Weldon, is a family physician and former Republican congressman from Florida, who has previously pushed disproven claims linking vaccines with autism.
Offit says there's a recent example of the director tweaking the policy recommendations. Dr. Rochelle Walensky, who served as CDC head early in the Biden administration, overruled the advisory committee in 2021 when she recommended COVID-19 booster shots to workers whose occupations put them at higher risk of COVID exposure, after the committee had voted against it. "Dr. Walensky went beyond what the ACIP voting members said, and did something she felt was important to do on her own. So ACIP is only so powerful," Offit says.
Besides overturning recommendations directly, the CDC director or other members of ACIP could also curb vaccine access by moving more vaccines from routine vaccinations people "should" get to those they "may" get if they and their doctors decide it's a good idea. This categorization, known as "shared clinical decision-making," softens a recommendation in the public eye and opens the possibility for some insurers not to cover the costs..
Could the administration disband the committee? "That's a bit of a grey area," says UC Law's Reiss. Federal committees are created by charter, and ACIP's charter is up for renewal in April 2026. "If the charter expires, or if the charter is abolished, they should cease to exist," she says.
But ACIP has been referenced in a few statutory provisions, such as its role in decision-making for the Vaccines for Children program. "The question becomes, who gets those powers if you abolish ACIP? Because the powers are still there and Congress hasn't cancelled those programs," Reiss says.
And it's possible to undermine the committee's credibility without dissolving it, Modlin says. "If you interfere with ACIP's process, people could lose confidence in the committee and its recommendations. You could reach a point where the function and advice of the committee means little to nothing," he warns.
And ACIP is just one of several policy levers controlled by the HHS secretary, says Katelyn Jetelina, an epidemiologist and author of the health newsletter Your Local Epidemiologist. HHS oversees the Food and Drug Administration as well, so Kennedy could change the review process for future vaccines, or revoke emergency use authorization for existing ones.
He might also work with other government agencies to withhold funding from school districts with vaccine mandates -- something Trump suggested on the campaign trail.
But the most immediate changes could come from the weight his words now carry, Jetelina says: "Continuing to sow doubt and confusion about vaccines from the most powerful office could profoundly impact Americans' ability to make evidence-based decisions in an increasingly noisy world."
Fewer people getting vaccines could mean that diseases currently under control could roar back.