The Centers for Disease Control and Prevention’s vaccine advisory committee is set to meet this week for the first time since Health and Human Services Secretary Robert F. Kennedy Jr. removed all of its sitting members and appointed new ones.

The Advisory Committee on Immunization Practices (ACIP) is expected to vote on vaccine recommendations for the fall as well as discuss other vaccines, including those given to children. The group wields enormous influence setting vaccine policy in the United States, including which vaccines will be covered by insurance.

Kennedy has long held many vaccine-skeptic views, refuted by experts and high-quality studies, long before he joined the administration, but he has insisted he is not “anti-vaccine” and rather “pro-safety.”

Kennedy, however, has begun removing guardrails protecting some pediatric vaccines. Some public health professionals are worried the ACIP’s upcoming recommendations will be part of Kennedy’s purported larger goal to reduce access to certain vaccines.

“He holds all of the reins, and he has an unbelievable ability to drastically change the access and availability of vaccines in this country, something that I and many others believe he is undoubtedly going to do,” Dr. Craig Spencer, an associate professor of the practice of health services, policy and practice at Brown University School of Public Health, told ABC News.

In a statement, an HHS spokesperson said, “Secretary Kennedy is restoring public trust by reconstituting ACIP with highly credentialed doctors, scientists, and public health experts committed to evidence-based medicine, gold-standard science, and common sense.”

Involvement with Children’s Health Defense

Years before becoming HHS secretary, Kennedy led Children’s Health Defense (CHD), a group that pursues anti-vaccine causes.

During his time as chair of CHD, Kennedy repeated unfounded claims that vaccines cause autism and that thimerosal, a mercury-based preservative that had been widely used in vaccines, was unsafe.

The group has continued to exert influence in anti-vaccine circles as seen during the measles outbreak in Texas this year, particularly among the Mennonite community.

CHD aired interviews with the two Mennonite families whose young children died from measles in the outbreak. In the interviews, both families claimed their children did not die from measles and said they did not support vaccination.

Kennedy has resigned from the board of CHD during his run for the presidency in 2023. But when Kennedy went to Texas in April to meet families affected by the measles outbreak, he shared two contradictory messages on X.

In the first post, Kennedy called the measles vaccine “the most effective way to prevent the spread of measles.”

In the second post later that evening, Kennedy said he met with two physicians who “treated and healed” about 300 children infected with measles in the Mennonite community with aerosolized budesonide and clarithromycin — a steroid and an antibiotic, respectively, and neither of which are treatments for measles.

“[Kennedy] basically came back to [CHD] to say, ‘Look, I had to put out a post of who they want me to be and who I’m supposed to be in this role. But here’s a post to show you all who I really am and what I’m really fighting for,’” Spencer said. “And I think that was really profoundly important for a lot of CHD people.”

RFK Jr. becomes HHS Secretary

During his confirmation hearings, Kennedy said he supports vaccines and that he is not “anti-vaccine” but “pro-safety.”

However, throughout the hearings, he refused to say that vaccines were not linked to autism, while still insisting he supports vaccination.

“So it does not appear that he supports vaccination by the actions he has taken and the statements he has made in the past,” said Dr. Jason M. Goldman, president of the American College of Physicians, ACP’s liaison to the ACIP, and a member of the college’s immunization committee and CDC-affiliated vaccine workgroups on pneumonia and COVID‑19.

“His statements seem apparently contradictory in trying to promote public health and welfare yet undercutting one of our very basic and foundational tools for prevention of disease,” Goldman added.

During his confirmation hearing, Kennedy also pledged not to remove the existing members of the CDC’s ACIP committee — a promise that was later broken when Kennedy removed its sitting members. The Biden administration had appointed all 17 sitting members of the ACIP, including 13 in 2024.

Open CDC Director Role

The Trump administration initially nominated Dr. David Weldon for CDC director, who was considered closely aligned with Kennedy and had previously stated the false idea that vaccines cause autism, a claim that has been long debunked by numerous, large-scale studies over the course of decades. His nomination was withdrawn after sources said he didn’t have the votes to be confirmed.

With the acting director position open, Kennedy has had final say over some CDC decisions. Sen. Lisa Blunt Rochester, a Democrat from Delaware, publicly called out the need to fill the open role in a May Senate hearing.

“Let me be clear: the absence of a CDC Director is a serious public health risk,” Blunt said in a statement. “The Director of the CDC has the sole authority to make critical decisions that affect millions of Americans. The Director is responsible for coordinating the response to emerging infectious disease outbreaks – which is now more important than ever, in the midst of our country’s largest measles outbreak in over two decades.”

Dr. Susan Monarez, the administration’s new pick for CDC director, will be at confirmation hearings this week.

“There is currently no acting CDC director, and so that means that these decisions all fall within the purview of RFK Jr.,” Spencer said. “He is able to do all of the things that only a CDC director would otherwise be able to do: to sign off on vaccines, to reconstitute ACIP.”

Changes around COVID vaccines

Prior to becoming HHS secretary, Kennedy spread misinformation during the COVID-19 pandemic, falsely claiming the COVID vaccine is dangerous.

Since he became head of HHS, there have been major changes at federal health agencies related to COVID vaccines.

In late May, the FDA announced it was planning to limit access to future COVID to those aged 65 and older and others with underling health conditions.

Additionally, the agency said it would allow vaccine manufacturers to conduct large studies to assess the safety and efficacy of COVID vaccines in children and younger, healthy adults.

About a week later, Kennedy cut COVD-19 vaccine recommendations for “healthy children and pregnant women” without a vote from the committee and posted the announcement on X rather than through official federal channels, in a break with tradition and stunning doctors.

“The decision to not allow pregnant women and children to get vaccinated based on a social-media post is not how science is conducted. And the second is the fact that he arbitrarily, unilaterally, without evidence, science, research or fact decides to change a vaccine schedule is abhorrent,” Goldman said.

Revamping ACIP

Earlier this month, Kennedy removed all 17 sitting members of the ACIP and appointed eight new members, some of whom have been critics of shots — especially during the COVID-19 pandemic.

The new eight members appear to have strong credentials related to medicine, public health, epidemiology and statistics, but with less of an emphasis on credentials related to immunology, virology and vaccinology in comparison with previous committees.

One of the new members, Dr. Robert Malone — who made some early contributors to mRNA vaccine technology — spread misinformation during the COVID-19 pandemic, claiming people were “hypnotized” into believing mainstream ideas about COVID-19, such as vaccination.

Retsef Levi, another newly appointed member, has previously published non-peer reviewed research alongside Florida Surgeon General Dr. Joseph Ladapo on COVID-19 vaccines, suggesting healthy people have died from the shots, claims that are not backed by evidence.

Goldman pointed out that he has served as a liaison to the ACIP for more than five years, helping review data and shape vaccine recommendations, but says he and other liaison committee members have been shut out of the process this time with no communication or access to meeting materials.

“What’s concerning to me is the process is not being followed. There’s no transparency. We’re not being given information,” he said.

In a statement, an HHS spokesperson said, “The Secretary has no intention of restricting access to vaccines, but to ensure all vaccines and medical interventions adhere to the highest standards of safety. Secretary Kennedy believes the American people deserve full transparency to make truly informed decisions about their health.”

The new members will be at the ACIP meeting and will vote on new recommendations for several vaccines, including RSV vaccines and influenza vaccines.

“The folks that were on ACIP prior to their forced resignation were all incredible, wonderful people, and they were all great scientists,” Spencer said. “Anybody that follows this [meeting] is going to see that it is a sham and a shameful process. It is a silly replacement for a process that was well-structured, well defined, and helped create guardrails of safety.”

It remains to be seen whether the new ACIP members will move to place further limits on existing vaccines.

ABC News’ Youri Benadjaoud and Sony Salzman contributed to this report.