Reflections on ACIP
Some thoughts on the June 25-26 2025 ACIP meeting
Hi, friends. Thanks for your patience with me. I know it’s been a minute since I’ve published anything on this blog. Recently, this has been because most of what I have written that would be of relevance to this blog has been done collaboratively with other subject matter experts in different fora (e.g., these briefs). Over the last 2 days, I watched the entirety of the ACIP1 meeting and documented them on my Bluesky.
Some context:
This ACIP meeting was very different from the ACIP meetings of the past- so much so that I will not be calling the current membership “ACIP” in this post because it is a mockery of the institution to do so. About 2 weeks ago, HHS Secretary Kennedy fired all 17 members of the ACIP, citing conflicts of interest as the reason (a lie) and replaced them with 8 new members, with one member (Ross) ultimately refusing to divest from stocks in pharmaceutical companies and therefore declining. Of these members, none are appropriate choices. One member (Cody Meissner) who clearly has the relevant expertise, has already served on ACIP, and, per norms (though not legally binding), ACIP members can only serve one term. Of the remaining members, the majority have not demonstrated any expertise relevant for such an important role, multiple members have extremely compromising, undisclosed conflicts of interest, and the rest are openly anti-vaccine and contribute to pollution of the information ecosystem accordingly. There are also signs that these members already violated laws pertaining to their conduct as members, specifically with off-record discussion of ACIP recommendations- something that has, historically, been enough to get advisory committee decisions overturned. Suffice it to say, ACIP can no longer be regarded as a legitimate body of expertise.
With this setup, the results are predictable and the goals are transparent, but I want to highlight a few specific aspects of the meeting.
Subversion of the process
The meeting had a few major outcomes:
The 2025-2026 flu vaccine formulation was recommended for all aged 6 months and older.
Clesrovimab, a new long-acting RSV monoclonal antibody recently approved by the FDA, was recommended for infants under 8 months and included in the Vaccines For Children program.
Thimerosal-containing flu vaccines (only multidose vials have it and they account for about 5% of all doses of flu vaccines given) were recommended to no longer be used
I’ll focus on the last outcome here. One of the most unsettling aspects of the meeting was the subversion of the process. It is very clear that the meeting was organized and designed to achieve a particular outcome with a predetermined conclusion, in particular, the removal of multidose flu vaccines that contain thimerosal. Normally, before ACIP votes on a recommendation, there is a specific process wherein CDC work groups who members work alongside present an Evidence to Recommendations (EtR) framework considering multiple domains:
whether the public health problem being addressed is an important public health problem (Problem)
whether the balance of benefits to risks is favorable (Benefits & Harms)
whether or not the target population for the intervention feels the benefits would outweigh the risks (Values)
whether or not the intervention would be acceptable to key stakeholders (Acceptability)
whether or not the intervention a reasonable and efficient allocation of resources (Resource Use)
how the intervention would affect health equity (Equity)
whether or not the intervention is feasible to implement (Feasibility)
Furthermore, evidence is evaluated according to the GRADE framework, which systematically evaluates the quality of the evidence and its importance to lend some objectivity to the evaluation process. Normally, going through these assessments is what takes up the majority of the time in ACIP meetings. It is a rigorous, evidence-based approach that, in principle, should give consistent conclusions. It is, in fact, gold-standard science.
But that’s not what happened in this meeting.
Apparently, it was decided that this entire framework could be thrown out and votes could be made on the basis of a single misleading, brazenly anti-vaccine presentation from Lyn Redwood, a former president of Children’s Health Defense (the antivaccine organization Robert F Kennedy Jr founded- a fact she did not disclose during the presentation), resurrecting decades-old canards about thimerosal having toxicities at doses relevant for vaccination (see this footnote for details about thimerosal2). To the credit of ACIP liaisons representing professional medical societies and voting committee member Meissner, there was significant pushback on this, which made note of the misleading nature of the presentation. Earlier versions of the presentation also had evidence of fake citations, suggesting the use of generative AI to create it and perfunctory laziness in verifying its accuracy. It would be very time-consuming to enumerate all of the problems with this presentation (I helped do that in the TEC brief), but, in brief, the presentation overwhelmingly relied on studies that were conducted before the toxicology of thimerosal was better understood (assuming it to be more or less equivalent to that of methylmercury), relied heavily on in vitro data in cell culture exploring mechanisms of thimerosal’s effects in cells, outright lied in some cases about what the data said, and actively avoided engaging with any of the clinical evidence showing thimerosal was not associated with harm. Upon receiving completely appropriate (and in my view far too gentle) pushback from attendees, Martin Kulldorff, the current chair of the committee, claimed that those criticizing the presentation were doing so because the presenter did not hold a doctoral degree- an issue that no one raised at any point. He furthermore justified that they did not need an EtR framework for evaluation of thimerosal in multidose flu vaccines because (I’m not kidding) Lyn Redwood is clearly very knowledgeable about vaccines.
This administration has spoken at length about the importance of gold-standard science. Presumably, evidence-based medicine is a part of that. What Kulldorff described is known as eminence-based medicine, which is essentially the exact opposite of evidence-based medicine wherein, instead of relying on the data, you simply defer all judgment to those you decide to be experts. Aside from this, given the numerous inaccuracies and deceitful nature of the presentation, Redwood cannot legitimately be regarded as someone very knowledgeable about vaccines unless we agree that delusions and facts are equivalent.
Boycotting by Professional Medical Societies
Some professional medical societies seemed to understand the moment, and refused to have liaisons present during the meeting. In particular, AAP, IDSA, SHEA, and SAHM all refused to attend. At one point, the MVP committee member (that bar is now a trip hazard in hell) Cody Meissner claimed that this move on the part of the AAP is “childish.”
I disagree. I think that move is a principled choice and the correct choice. The reality is that most people do not live and breathe vaccines, medicine, or public health as some of us do, but the endorsement of ACIP recommendations by medical societies grants them legitimacy. Even for someone who is not really paying attention, the uniform rejection of this committee (I don’t even think they can properly be called ACIP anymore) on the basis of its policy-based evidence-making approach to recommendations, its refusal to appoint qualified members, its open embrace of conflicts of interest- it does not deserve symbols of legitimacy. It does not deserve the presence of professional medical societies.
What AAP did was not only correct, but it is an example that every single professional medical society should follow. One of our most important advisory committees -one that makes life-or-death decisions for 330 million people- has been hijacked by ideologues who are actively trying to destroy the US’s vaccine infrastructure, and judging by recent events, the world’s as well.
The AAP has announced that it will be posting its own childhood vaccination schedule, as it has done before the ACIP was formed in the 1960s. I would like to see more efforts like these coordinated across multiple medical societies with relevant subject matter experts (such as ACOG, SMFM, IDSA, PIDS, APhA, ACP, APHA, NAPNAP, AIM, GSA, etc.) to ensure harmonization of guidelines. AHIP has announced that insurers will continue to cover vaccines, though, notably, this does not apply to Medicare, Medicaid, or the Vaccines For Children Program.
The Professionalism of CDC Staff
In some sense, it seems silly to say this because it is literally their job, but the CDC staff who presented during the meeting did an excellent job with their presentations, which were meticulously prepared, highly informative, and well-suited to address concerns that the public may have and that the actors on Kennedy’s committee seek to foment. In particular, Drs. Meyer, MacNeil, and Link-Gelles did a spectacular job, though all of the presenters (excluding Redwood and Kuldorff) were excellent. I think that the juxtaposition of these staff and the committee members was critical because it made something abundantly clear: this committee is profoundly unqualified to assess anything to do with vaccines, and it was not subtle about that.
For example, when we consider the effectiveness of COVID-19 vaccines, we generally use test-negative studies in which people presenting for COVID-like illness for care are identified and then compared by vaccination rate (this allows you to control for care-seeking behavior- a critical bias). As a methodological constraint however, individuals who tested positive for RSV and influenza were excluded from these studies. FDA Liaison Tracy Beth Hoeg, an epidemiologist (studying ophthalmology) and sports medicine physician with no specific expertise in vaccines despite frequent opining about them during the pandemic, raised the point that this could introduce bias into the measurements of effectiveness. In fact, the opposite is true because influenza and RSV vaccination status associate strongly with COVID-19 vaccination status, as Dr. Link-Gelles explained during the meeting. Then there was the incredible moment when voting member Retsef Levi didn’t seem to understand that more deaths in a group that received an intervention (in this case nirsevimab) with 2:1 randomization is expected and there is no genuine imbalance in mortality, and when he ignored the presentation on nirsevimab safety in a study in the Vaccine Safety Datalink covering 36,719 infants which found no increased risk for any targeted outcome among recipients of nirsevimab. He then proceeded to vote against the use of clesrovimab for infants under 8 months of age in part because he believed that they weren’t high-risk after presentations and ACIP member Meissner had explained that all infants are at high-risk for severe RSV, but did vote to approve its coverage under the Vaccines For Children program.
CDC staff, in preparation for the deluge of falsehoods and misrepresentations, posted pre-bunks for thimerosal and MMRV as well, though these were quickly taken down from the website- but you can view them here and here.
In sum, the committee meeting was the farce that anyone who knows anything about these actors would expect it to be. The current committee advising on immunization practices should be regarded as irrevocably compromised in its current form and should not be regarded as making good-faith attempts to protect the health of the millions of Americans that it is its remit to serve. Still, it was also useful in helping to establish the next best course of action:
Professional medical societies should not lend their presence to the meetings or make attempts to collaborate with this committee.
Professional medical societies should collaborate together to harmonize a vaccine schedule based on evidence, starting from the data to get to recommendations, not the inverse.
We will have to do much continued work to ensure access to vaccines for the US population, requiring extensive collaboration with payers and likely creative problem-solving for those beholden to public insurance or the VFC for access (as those are tied to ACIP recommendations).
CDC staff deserve our support for their tireless work in trying times.
ACIP is the Advisory Committee on Immunization Practices. Historically, it has comprised a group of experts in fields relevant to vaccines (infectious diseases, medicine, epidemiology, immunology, virology, pediatrics, OBGYN, gerontology, etc.) who undergo extensive vetting for conflicts of interests (it generally takes over a year to validate that they do not have conflicts of interest). These experts are special government employees and they make recommendations for how a vaccine (or in more recent years, long-acting monoclonal antibody) should be used once it has already been approved (licensed) by the FDA. Ultimately, their recommendations have to be signed off by the CDC director to be put into effect, and the CDC director may choose to modify them, but, in general, the recommendations made by ACIP are the ones that go into effect. The work of ACIP is critically important for public health because their recommendations determine access to vaccines, and insurance coverage for vaccines. Additionally, before the ACIP existed, multiple professional medical societies published their own vaccine schedules, at times resulting in discrepancies between societies and making it hard for clinicians on the front lines to know which schedule to follow. With the establishment of ACIP in the 1960s, these recommendations were harmonized across professional medical societies.
Context: thimerosal is a preservative (it works to prevent microbial contamination) when using multidose vaccine vials. This is important because each time a dose of vaccine is drawn up from a multidose vial, microbes can be introduced into the vaccine, and this can lead to infections when vaccinating, which in some cases have been fatal. The use of preservatives prevents this. Thimerosal may also be an inactivating agent in some vaccines (used to inactivate microbes). Decades ago, as a fraudulent link between vaccines and autism was proposed, thimerosal was singled out as a possible culprit because thimerosal rapidly breaks down into ethylmercury and thiosalicylate, and mercury is known to be neurotoxic. This line of thinking lacked plausibility, however, because the neurological manifestations of mercury toxicity manifest in very different ways from how autism presents. In the 1990s however, a concern was raised in that, using the EPA’s limits on prenatal exposure to methylmercury (the kind you find in seafood), exposure to thimerosal through the vaccination schedule would exceed those limits (the quantities, however, were still below FDA and ATSDR thresholds). By 2001, the FDA and vaccine manufacturers worked to remove all thimerosal from routine childhood vaccines, and the last doses of these vaccines expired in 2003. Today, (in the US) thimerosal is present only in multidose flu vaccines which make up about 5% of all flu vaccines given, and it may occur in trace amounts (that is, quantities too small to be measured accurately) with the TDVax vaccine (but not other tetanus or diphtheria vaccines). However, in the wake of all of these precautionary measures, research began to trickle in. Massive independent epidemiological studies across diverse populations showed no link between thimerosal and neurodevelopmental outcomes. In fact, despite the removal of thimerosal from various countries’ vaccines, autism rates continued to increase. Additionally, people began to systematically examine the toxicology of thimerosal and found that ethylmercury from thimerosal did not behave the same way as methylmercury- it was eliminated much more quickly from the body, and thus had minimal potential to accumulate to toxic levels. However, the elimination of thimerosal from routine childhood vaccines, though done out of an abundance of caution and later proven unnecessary, had the unfortunate effect of validating that fear of thimerosal was a legitimate concern.