This week's meeting of the Advisory Committee on Immunization Practices (ACIP) is likely to mark its end—for now—as a vaccine advisory body.
Regardless of which party controlled the White House and who served as secretary of the Department of Health and Human Services (HHS), ACIP—a federal advisory committee of the US Centers for Disease Control and Prevention (CDC)—held meetings that included presentations of vetted, evidence-based data and used a structured framework for moving from scientific evidence to vaccine recommendations.
Based on what we have learned about the new committee members appointed by the secretary, the meeting agenda and presenters, however, the purpose of the meeting appears to be an opportunity to deemphasize vaccine benefits—many of which are largely invisible to the public and taken for granted—and emphasize the potential risks of vaccines.
If that proves true, the meeting could succeed in its apparent goal of discouraging vaccination, putting more people at risk of vaccine-preventable illnesses. Concern about the legitimacy of the meeting has risen to the point that Senate Health, Education, Labor and Pensions Committee Chairman US Sen. Bill Cassidy, R-LA, tweeted that it should be postponed.
The members and the structure
By now, the concerns about ACIP members who were recently appointed by HHS Secretary Robert F. Kennedy Jr. are well known. The members' conflicts of interest, anti-vaccine activism, and a general lack of experience have all been noted in the news media and scientific journals. These facts are added to the ledger with Kennedy's own long history of anti-vaccine activism. "Otherwise, ACIP's recommendations could be viewed with skepticism ..." Cassidy tweeted, citing concerns about the qualifications of recently appointed members.
Troubling, too, are changes to how ACIP typically operates. Remarkably, Lyn Redwood, the president emerita for the anti-vaccine group Children's Health Defense, is slated to provide a presentation. Additionally, this will be the first meeting with presentations that CDC subject matter experts did not vet. Their eyes haven't touched the scheduled presentations on the flu vaccine and thimerosal, which Redwood is slated to give, or the measles, mumps, rubella, and varicella (MMRV) vaccine. These are clear signs that the true intent of the meeting is to sow distrust about the safety of vaccines.
Lyn Redwood, the president emerita for the anti-vaccine group Children's Health Defense, is slated to provide a presentation.
Meanwhile, the preparation for a typical, public ACIP meeting includes CDC "work groups" reviewing relevant data to develop recommendation options for the voting members. But work group planning meetings were postponed, because voting members were fired by Kennedy.
Gone, too, is the official who oversaw the meeting's planning and agenda—a seasoned vaccine expert with three decades of federal vaccine experience spanning all administrations since 1992. She was replaced by a government official who reports to the agency's political chief of staff and leads administrative tasks, such as scheduling for the CDC director.
Meanwhile, votes on vaccine recommendations for adult respiratory syncytial virus, COVID-19 and human papillomavirus vaccines have been postponed.
An unbalanced display of data
In any balanced discussion of vaccines, the data include both a comment on their risks and their benefits.
This week's ACIP’s agenda includes presentations on thimerosal and flu vaccines and the risk of febrile seizures related to the MMRV vaccine, but it does not appear to include any discussion of the benefits of vaccination against these preventable illnesses. The diseases prevented or mitigated by these vaccines pose a clear—but not always apparent—threat to Americans' health.
The flu vaccine and the anticipated thimerosal presentation
In the 2023-24 season, the CDC estimates "that flu vaccination prevented 9.8 million flu-related illnesses, 4.8 million medical visits, 120,000 hospitalizations, and 7,900 deaths." Even so, in that same respiratory virus season, for example, more than 200 children died from flu, over 80% of whom were unvaccinated.
During the most recent flu season, the preservative thimerosal was used in a small percentage of flu vaccines, confined to multidose vials. Thimerosal has long been a focus of anti-vaccine activists and the genesis for attempts to connect vaccines with autism. As a congressman, former CDC director nominee Dave Weldon raised concerns about it and fanned worries about autism that are not supported by evidence and may have been among the reasons for his failed nomination. His former chief of staff, Stuart Burns, is now a high-ranking political appointee at the CDC.
Thimerosal has been closely studied as a vaccine preservative—a role it has played since the 1930s. The preservative—which contains the rapidly cleared ethylmercury, often confused with the slowly cleared and therefore toxic methylmercury—has been used for multidose vials to prevent multiplication of bacteria or fungi that might occur from the repeated introduction of a syringe. Over two decades ago, the CDC and the American Academy of Pediatrics asked vaccine manufacturers to remove the chemical over public concerns that it might lead some people to choose not to vaccinate, and because it was feasible without affecting the US vaccine supply. Subsequent review of nearly 40 years of published studies found no connection to developmental disabilities.
Data from many studies show no evidence of harm caused by the low doses of thimerosal in vaccines.
Today, CDC's website states, "Thimerosal use in medical products has a record of being very safe. Data from many studies show no evidence of harm caused by the low doses of thimerosal in vaccines."
Even though the prevalence of thimerosal in flu vaccines is low and it hasn't been linked to developmental issues, the public confusion and over ethylmercury remains—confusion that anti-vaccine activists, such as Lyn Redwood, have sought to stoke.
The MMRV vaccine and the anticipated presentation on febrile seizures
Not on the schedule for ACIP review this week is the benefit of measles vaccination, even in the midst of the second largest measles outbreak—including two pediatric deaths—in the United States since measles was declared eliminated in 2000.
The protective effects of the measles, mumps, and rubella (MMR) vaccine are dramatic. According to a recent CDC study, from 1994 to 2023, this combination vaccine prevented 13 million measles-related hospitalizations in the United States. (The MMR vaccine additionally averted more than 2 million hospitalizations and 700 lives from mumps and rubella).
While we're unlikely to hear the new ACIP members talk about the benefits of vaccination, and the vaccine's success has all but ensured that the diseases they combat have faded from the public's everyday concerns, there is a scheduled session that is likely to highlight vaccine risks.
To unpack the details, there are two combination vaccines for measles: MMR and MMRV. The latter, licensed in 2005, was meant to reduce the number of injections, improve vaccine coverage, and increase convenience by adding the varicella vaccine to the already co-formulated MMR vaccine.
Two and a half years after the introduction of MMRV, in a public meeting in February 2008, the ACIP reviewed preliminary post-license data showing a twofold increased risk of febrile seizures associated with its use. It wouldn’t be surprising if this was the focus of the MMRV discussion. The ACIP updated its guidance at the time to remove the preference for the MMRV vaccine.
The 2008 meeting highlighted the fact that, while the absolute risk was low, according to a large and later published (2010) study, the first dose of MMRV vaccine in toddlers added roughly four excess seizures per 10,000 doses. Children who experienced a seizure related to MMRV vaccination were not at increased risk of neurodevelopmental disorders or epilepsy than children who experienced it otherwise, and no increased risk was seen in older children.
In June 2009, ACIP recommended the separate administration of MMR and varicella vaccines for children 12 to 47 months old, unless a parent expresses a preference for the MMRV vaccine. Physicians are also encouraged to discuss risks and benefits with caregivers.
New, worrisome focus for ACIP
Why then is ACIP taking up these two issues? It is possible that there are new data, but CDC experts with decades of experience haven't seen them.
The other explanation, supported by Kennedy's anti-vaccine activism and the backgrounds of the new ACIP nominees, is that the goal of the meeting is to put greater focus on and generate more public discussion about vaccine risk. We already have evidence that Kennedy does not view ACIP as a necessary part of vaccine recommendations, as he went around the body when he rescinded, without supporting evidence, the recommendation for COVID vaccination for children and pregnant women.
It is possible that there are new data, but CDC experts with decades of experience haven't seen them.
If this week's meeting is little more than an attempt to give discredited vaccine fears and long-solved problems a platform—trading on a committee name that has stood for deliberate, evidence-based decision making—the American people would do well to tune it out. It will serve as further evidence that vaccine information and recommendations—at least temporarily—need a new home, a home outside the current HHS Secretary's purview.
Vaccine Integrity Project Viewpoints are authored by project staff and advisers. They are intended to address timely issues regarding vaccines with straight talk and clarity by presenting facts to counter falsehoods.
