Background

Earlier this month, HHS Secretary Robert F. Kennedy Jr. fired all 17 members of ACIP, arguing in an opinion piece for the Wall Street Journal that ACIP was "plagued with persistent conflicts of interest and has become little more than a rubber stamp for any vaccine," adding that ACIP has "never recommended against a vaccine — even those later withdrawn for safety reasons" and "failed to scrutinize vaccine products given to babies and pregnant women."

Days later, in a post on X, Kennedy named the eight doctors and researchers who would be part of ACIP, saying his picks included "highly credentialed scientists, leading public-health experts, and some of America's most accomplished physicians." All of Kennedy's picks are either medical doctors or doctorates.

Before ACIP's first meeting, Michael Ross, a physician in Virginia and former professor of obstetrics and gynecology, withdrew from ACIP. It's unclear why Ross stepped down, but HHS spokesperson Andrew Nixon said that Ross "decided to withdraw from ACIP during the financial holdings review required of members before they can start work on the committee."

"The sacrifice to serve on ACIP varies from member to member, and we appreciate Dr. Ross's willingness to go through this rigorous process," Nixon added.

ACIP says it will review childhood vaccine schedule

At the start of its meeting, Martin Kulldorff, an epidemiologist formerly at Harvard Medical School who now serves as chair of ACIP, called for the need to "rebuild public trust" in federal health institutions in the wake of the COVID-19 pandemic and what he referred to as the "inflated promises" about the COVID-19 vaccines and mandates.

As a result, Kulldorff said that ACIP would establish a new workgroup to study and evaluate the effects of the recommended vaccine schedule, including the "interaction effects between different vaccines, the total number of vaccines, cumulative amounts of vaccine ingredients and the relative timing of different vaccines."

"The number of vaccines that our children and adolescents receive today exceed what children in most other developed nations receive and what most of us in this room received when we were children," Kulldorff said.

Kulldorff added that another new workgroup will specifically look at "vaccines that have not been subject to review in more than seven years," including the recommendation to administer the hepatitis B shot on the day of birth, how children are immunized against measles, mumps, rubella, and varicella, or chicken pox, and the timing of the measles vaccine to resolve religious objections from some parents.

CDC experts emphasize importance of COVID-19 vaccination during pregnancy

During ACIP's meeting, experts from CDC emphasized the importance of all children ages six to 23 months and people ages two to 64 at high risk of severe COVID-19 being vaccinated, including pregnant women.

Last month, Kennedy ended CDC's recommendation to vaccinate children and pregnant women against COVID-19.

During the presentation, Adam MacNeil, from CDC's National Center for Immunization and Respiratory Diseases, showed that hospitalization rates in the 2024-25 season were the highest among adults ages 75 and older, followed by adults ages 65 to 75 and children under 6 months, who had similar hospitalizations rates.

ACIP recommends all Americans get annual flu vaccine, recommends against use of thimerosal

On Thursday, the panel heard a presentation on the use of the use of the preservative thimerosal in some flu vaccines from Lyn Redwood, a former leader of the anti-vaccine group Children's Health Defense, which Kennedy co-founded.

In the 1930s, vaccine makers used thimerosal to stave off microbial growth in their products, and the preservative was used for the next 60 years without much notice. However, in 1999, U.S. health officials asked pharmaceutical companies to remove the preservative from vaccines. While there wasn't any evidence thimerosal caused harm in the quantities used, the preservative contains a form of mercury, and there were questions over whether it could cause neurotoxicity when used in childhood vaccines.

"While there was no evidence of harm from thimerosal, the general feeling was, 'let's get rid of it, because we don't need it,'" said Walter Orenstein, who was director of CDC's National Immunization Program at the time.

That led to several studies on the issue, including one 2004 assessment from the Institute of Medicine — now known as the National Academy of Medicine — that concluded "the body of epidemiological evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism." A 2010 study from CDC also found no link between thimerosal and autism rates.

Currently, the preservative is present in "a small percentage of flu vaccines, confined to multidose vials," according to the Vaccine Integrity Project. During the 2024-25 respiratory virus season, just 3% of children and 2% of older adults received a flu vaccine containing thimerosal, according to an analysis of electronic health records by Truveta.

During the meeting, Redwood claimed that thimerosal was toxic to the brain and refuted claims that there has been no proven harm from the preservative in vaccines.

She received pushback from Cody Meissner, a pediatrician who teaches medicine at Dartmouth University's Geisel School of Medicine and the only pediatrician on ACIP, who said there "is no scientific evidence that thimerosal has caused problems," adding that the "risk for influenza is so much greater than the non-existing risk from thimerosal."

Meissner said that vaccines with thimerosal are metabolized as ethylmercury rather than methylmercury, which is a form of mercury found in fish and shellfish and known to be a neurotoxin.

"I'm not quite sure how to respond to this presentation," Meissner said. "This is an old issue that has been addressed in the past. Ethylmercury is excreted much more quickly from the body. It is not associated with the high neurotoxicity that methylmercury [is]."

Still, ACIP voted 5-1, with Meissner voting against, to recommend against flu vaccines containing thimerosal. Shortly before the vote, ACIP voted 6-0 to recommend that all Americans ages 6 months and older receive an annual influenza vaccine. One member of the panel, Vicky Pebsworth, abstained from each vote.

ACIP recommends preventative therapy for RSV in babies

In a 5-2 vote, ACIP recommended the use of a new preventative therapy for RSV in babies, a monoclonal antibody given to babies under 8 months of age entering their first RSV season.

The therapy, called Enflonsia and developed by Merck, was approved by FDA in early June. The monoclonal antibody injection was shown to reduce the rate of medically attended lower respiratory infection caused by RSV by over 60% and reduced the incidence of RSV hospitalizations by over 84%.

During the meeting, Meissner emphasized the need for tools to lower the burden of RSV infections, which are the leading cause of hospitalization of children in the United States.

"These are truly remarkable products," he said. "They are safe and they are effective."

Following the initial vote, the panel voted unanimously to recommend that Enflonsia be added to the list of interventions accessible through the Vaccines for Children Program.

Recommendations from ACIP must be approved by the CDC director or health secretary to take effect. Currently, there is no CDC director and whether Kennedy will endorse the recommendations is unclear.