First Meeting of New ACIP Committee Touches on RSV, Thimerosal, mRNA Vaccines and More

Following the thimerosal debate, ACIP members voted on a series of recommendations on influenza vaccines for the upcoming season. ACIP makes recommendations to the CDC but the CDC is not obliged to follow them, though the agency often does.

The first vote reaffirmed ACIP’s recommendation that all patients 6 months of age or older who don’t have contraindications should receive an influenza vaccine. The committee voted 6-0 in favor of this recommendation. Meissner voted yes while adding that “there are very few contraindications for receiving flu vaccinations.” Pebsworth abstained because of a procedural concern.

The next vote was on an ACIP recommendation that anyone 18 years or younger receive an influenza vaccine in a single-dose formulation without thimerosal. The vote was 5-1 in favor, with Meissner the lone dissent. Pebsworth had technical issues, was skipped for the vote and then reappeared to reiterate she is abstaining by choice. Despite holding healthcare stocks, she insisted she is “allowed to participate.”

The committee then voted on a similar recommendation, that pregnant women also receive a single-dose influenza vaccine without thimerosal. The vote was 5-1 in favor, with Pebsworth again abstaining and Meissner voting no.

The final vote was a recommendation that all adults receive a seasonal influenza vaccine without thimerosal. The vote was again the same, 5-1 in favor, with Pebsworth abstaining and Meissner voting no. Hillbern commented after this final vote that he still supports the use of multidose vials and hoped that the committee would consider other preservatives.

After the voting concluded, Meissner asked for a chance to speak.

“My concern is that by insisting that vaccine doses not contain thimerosal, that might lower vaccine access,” he said. “The risk from the flu is so much higher than [from] thimerosal, I would hate for someone not to receive the vaccine because it does contain thimerosal.”

After Kulldorff concluded by thanking the committee members and the public, Meissner again asked to speak and commented that the American Academy of Pediatrics’ decision to boycott the meeting was “childish.” The AAP, which decided not to attend the meeting after Health Secretary Robert F. Kennedy Jr. fired the committee’s previous 17 members, has said it will publish its own vaccine recommendations parallel to ACIP’s.

“I’m led to believe that they didn’t want to come because they didn’t want to defend their views,” Meissner added, saying that the group has been helpful to the committee in the past and recommended that it participate in the next meeting.

“I am presenting as a private citizen and not representing any federal agencies,” Lyn Redwood offers as a disclaimer prior to her much anticipated presentation on the use of thimerosal in vaccines. Redwood spent years as the president of the Children’s Health Defense, an anti-vaccine group founded by HHS Secretary Robert F Kennedy Jr. She is at this week’s ACIP meeting advocating for the removal of thimerosal, an ethylmercury-containing preservative, from influenza vaccines.

In her presentation, Redwood recapped the history of thimerosal, which was almost entirely removed from available vaccines 25 years ago: currently, 94% of influenza vaccines in the U.S. do not contain thimerosal. She suggested that thimerosal was never tested and grandfathered into approval by the FDA.

Redwood presented data on the toxicity of thimerosal to cells and efficacy of the preservative, stating that studies had found it was not effective to limit bacterial or fungal growth. She concluded that “the only feasible and cost-effective preventative measure [for preventing bacterial contamination] is careful attention to sterile technique when administering vaccines for multi dose vials.”

Redwood’s presentation elided the difference between methylmercury—widely recognized as poisonous—and ethylmercury, the form of the atom in thimerosal, which is processed and excreted more quickly from the body than methylmercury. The CDC itself states that thimerosal is safe.

ACIP member Cody Meissner chimed in, saying “this is an old issue.” He reiterated that ethylmercury is excreted from the body more quickly than methylmercury and is not associated with neurotoxicity. Meissner appeared frustrated by Redwood’s presentation, adding that vaccines for children and pregnant women are already available without thimerosal.

“Of all the issues that ACIP needs to focus on, this is not a big issue,” Meissner said.

Thimerosal had been used as anti-fungal and anti-bacterial agent in vaccines since the 1930s. Its use allows multiple people to be vaccinated safety from a single vial, which are cheaper and easier to transport than single-dose packages. Anti-vaccine advocates began suggesting in the 1990s that because thimerosal contains a mercury atom it is linked to autism and neurotoxicity. The CDC itself has stated that there is no link between the preservative and either autism or neurotoxicity.

While it is little used today in the U.S., Meissner pointed out that thimerosal is included in most vaccines administered around the world, as many countries cannot afford single dose vials. “I know that ACIP is focused on the United States, but the recommendations that ACIP makes are followed around the world. Removing thimerosal from all vaccines used in other countries is going to reduce access to these vaccines, it will increase costs, and I think it’s important to note that no study has ever indicated any harm from thimerosal.”

However, he reiterated his stance: “I don’t think this is an issue.”

Redwood responded by stating that there are other preservatives that vaccines could use, like 2-phenoxyethanol, which is already used in some vaccines.

Meissner said there is no scientific evidence that thimerosal causes a problem, and that 2-phenoxyethanol and other preservatives that Redwood suggests have not been studied as much as thimerosal.

Vicky Pebsworth, who has been relatively quiet during the meeting so far, suggested that because women in early pregnancy could receive a vaccine with thimerosal, ACIP should phase it out as a “precautionary principle.”

Retsef Levi, who on the other hand has been extremely talkative, said that although evidence indicates individual vaccines containing thimerosal are not harmful, saying they haven’t caused harm “is a tricky issue.” He said that clearly there is harm based on cumulative effects. Kulldorff concurred.

Joseph Hibbeln argued that there is no demonstrated cumulative effect. “The precautionary principle is not a mandate for us to make decisions,” he said.

The committee then opened the floor to public comment, during which Stacy Buchanan, representing the National Association of Pediatric Nurse Practitioners, pointed out that no pediatric vaccines contain thimerosal, and that only three products listed on FDA website for multidose vaccine products contain the preservative.

A naturopathic doctor called in to say that “removing thimerosal does not make vaccines safer, just more expensive. The litigation of questions already thoroughly answered, like the safety of thimerosal, is not advancing radical transparency. It is an insidious attempt to suggest that something was missed or hidden previously.”

After recommending Merck’s new RSV antibody, ACIP moved on to discuss the upcoming influenza season.

The committee heard presentations from Vivien Dugan, the head of the CDC’s influenza division, and Pedro Folegatti, global clinical development director at Sanofi Pasteur. Folegatti described the efficacy of a recombinant influenza vaccine, FluBlok quadrivalent, covering four different circulating strains of the influenza virus. FluBlok is manufactured by Sanofi.

This section of the ACIP meeting involved less debate than some of yesterday’s presentations. Cody Meissner asked some technical questions about the seroconversion of vaccines, while Robert Malone asked about the fluctuating presence of different flu strains throughout the COVID-19 pandemic. The meeting then moved on to Lyn Redwood, from the known anti-vaccine group the Children’s Health Defense, and her presentation on the preservative thimerosal—a topic that is sure to elicit some lively discussion.

On Wednesday, the CDC’s Advisory Committee for Immunization Practices ran out of time before two scheduled votes on respiratory syncytial virus medications. Tacking the votes onto the beginning of the second day, the committee approved a recommendation for Merck’s monoclonal antibody Enflonsia to cover babies less than eight months who are not protected by maternal antibodies. Enflonsia itself won FDA approval just two weeks ago.

“I move for approval of this draft recommendation language, over,” Robert Malone said.

The vote was 5-2 in favor of the recommendation, with Retsef Levi saying he did not think the shot was ready for recommendation, and Vicky Pebsworth voting no without explanation.

The second vote was on an updated Vaccines for Children (VFC) resolution for preventing RSV, which would make Enflonsia available in the VFC program. VFC is a federally funded program that began in 1993 to provide vaccines to children without health insurance.

“It is extremely important that VFC cover this product. It is very important to ensure equity so that all children have access to these monoclonal antibodies,” Meissner said.

The vote on Enflonsia access in VFC was 7-0, including Levi and Pebsworth.

In 2023, Sanofi and Novartis won FDA approval for their jointly developed monoclonal antibody, nirsevimab, marketed as Beyfortus, for the treatment and prevention of respiratory syncytial virus (RSV).

Adam MacNeil returned to speak about RSV, saying that nearly all children are infected by age 2, and that 2%–3% of those children are hospitalized because of that infection. Most children have no underlying conditions.

“In short,” MacNeil said, “all young infants are at risk from RSV.”

The good news in MacNeil’s review of Beyfortus’ effectiveness in newborns and infants is that the numbers are overwhelmingly positive. The CDC epidemiologist presented data showing that 57% of infants born in the last year were protected either by an RSV vaccine received by their mother or via Beyfortus treatment.

Data from two different real-world trials showed that Beyfortus was about 80% effective at preventing hospitalization among infants in their first RSV season.

Two of the more talkative ACIP members, Robert Malone and MIT professor Retsef Levi, both asked questions about the effectiveness of monoclonal antibodies. MacNeil responded by saying RSV is such a common and pervasive virus—most humans are infected multiple times during their lives—that evolutionary pressure on the virus is small and so antibodies are thought to remain effective for some time.

Another chatty member, Cody Meissner, chimed in, calling the results “spectacular” and “an astonishing accomplishment.”

Just two weeks ago, Merck’s monoclonal antibody for RSV, Enflonsia, won FDA approval, giving healthcare providers a second option for treatment. GSK, Pfizer and Moderna all have RSV vaccines available, though current CDC guidelines recommend those vaccines mostly for the elderly.

Day one of the meeting concluded with public comments from ten individuals with a variety of viewpoints on vaccines. The overwhelming majority, however, condemned Health Secretary Robert F. Kennedy Jr.’s decision to oust the entire 17-member ACIP panel earlier this month.

“Was it necessary to purge this panel of all 17 duly vetted experts?” asked one individual, a self-described lay person. “Was it because, according to Dr. [Marty] Makary, ACIP is a kangaroo court that rubber stamps, or was this purge unjustified and unthinkable?”

Another commenter, a pediatric nurse practitioner of over 30 years, said the scientific, medical and public health communities are losing faith in the ACIP because of the “bogus reasons” that were used to dismiss the 17 members.

“Those members have the expertise to design vaccine studies. It is clear that the current members do not have this expertise,” she said.

Caroline Brown, a general pediatrician from North Carolina, focused on Thursday’s presentations on the use of thimerosal in vaccines.

“The fact that thimerosal is on the agenda for tomorrow’s meeting is particularly concerning, given that it was removed from virtually all routine pediatric vaccines in this country over 20 years ago,” she said. North Carolina just registered its first confirmed case of measles this year, Brown added.

“We must acknowledge that measles spread throughout our country is our reality today only because of the fear-mongering and pseudoscience that has overtaken our country,” she said. “Remember, measles was completely eradicated from the United States 25 years ago, and is back now because of declining vaccine rates, fueled by misinformation that is not only allowed, but amplified by the voices of some of you sitting on this very committee.”

A dissenting opinion came from Kim Mack Rosenberg, general counsel at Children’s Health Defense, an anti-vaccine advocacy group founded by Secretary Kennedy, who implored ACIP to affirm that CDC is not authorized to give medical advice with respect to what a particular child may require to stay safe.

Following MacNeil was Sarah Meyer, the director of the CDC’s Immunization Safety Office. Her presentation covered the safety of COVID-19 vaccines, focusing on the mRNA vaccines developed by Pfizer/BioNTech and Moderna.

According to Meyer’s presentation, 17,631 deaths were reported to the Vaccine Adverse Event Reporting System (VAERS) following COVID vaccination. After noting that VAERS does not assign causality to the events reported to it, Meyer presented results of a data analysis showing that deaths following mRNA vaccination were below the background death rate for the U.S. population. This indicated that mRNA vaccines are not dangerous but in fact protective, she said.

In the Q&A section, Robert Malone—an early mRNA vaccine researcher turned skeptic—questioned the safety of mRNA vaccines, suggesting that mRNA epitopes stay in the body for upwards of “700 days.” That statement is contradicted by an overwhelming body of evidence, which has shown that mRNA vaccines are destroyed by the body within a few days, persisting at most for about 30 days.

Vicky Pebsworth, speaking for the first time in this meeting, said without elaborating that many adverse effects from mRNA vaccines are not reported. Meyer responded that most unreported adverse effects are for mild effects like sore arms, but that CDC studies show most serious adverse effects are in fact reported.

“For those serious events, we are confident that we get a majority of those reported to VAERS,” she said.

After the introductions, Kulldorff said that upcoming ACIP work groups would look at cumulative childhood vaccine schedules as well as the adolescent schedules. This includes reconsidering giving newborns a vaccine for hepatitis B, which the CDC currently recommends for all infants. The American Academy of Pediatrics recommends the vaccine for newborns within 24 hours of birth.

“An argument could be made for delay of vaccine for this infection, which is primarily spread by sexual activity and intravenous drug use,” Kulldorff said.

Addendum: While common perception of hepatitis B is that it only transmits through sexual contact or needle usage, horizontal transmission is a major factor in hepatitis B infections. For example, one study found that the vast majority of hepatitis B infections in a family can be attributed to simple exposure to an infected person.

The meeting’s first presentation was given by Adam MacNeil, a supervisory epidemiologist at the CDC. He gave a presentation on COVID-19 epidemiology and vaccine effectiveness, recapping the current CDC recommendations for who should get COVID-19 vaccines. As it stands now, the agency recommends essentially everyone older than six months of age get vaccinated, though in May 2024 the CDC changed its recommendation for healthy children to be a “shared clinical decision,” including parental input.

MacNeil’s data presentation showed that vaccine uptake across the U.S. population is rather low, at about 25% for most adults and peaking slightly north of 30% for some sub-groups aged 65 or older. The data further showed that for children aged 2 to 17, hospitalizations due to COVID-19 were low, but children six months or younger were hospitalized at about the same rate as adults aged 65–74 years.

MacNeil reported about 21,000 deaths over the past year, the cause of which was listed on death certificates as COVID-19, though he noted that this is likely an underestimation, with a suggested death rate of 32,000–51,000 based on surveillance data.

In a Q&A session after MacNeil’s first presentation, several members of the committee questioned MacNeil’s data, particularly the death rate figures. Cody Meissner suggested that some patients who were listed as having died from COVID-19 might have died of something else while also having a COVID-19 infection.

“Like people who have appendicitis and happen to have positive PCR result,” Meissner said. “As we know, asymptomatic colonization is quite common with this virus.”

MacNeil and a second expert pushed back, noting that results were limited to where COVID-19 was the “likely reason for admission,” noting that recent work from CDC could accurately identify which patients were hospitalized and died because of COVID-19 and not just having a coincidental infection alongside something else, due to testing positive for COVID and having COVID-related symptoms like pneumonia.

“This is a rare disease,” Meissner said, pointing to dropping rates of infection over the last few years.

COVID-19 is “still a substantial burden,” MacNeil responded, noting high rates of long COVID and that COVID-19 far outpaces other respiratory diseases in hospitalizations because the disease infects year-round, unlike influenza and RSV, which are much more seasonal.

“Opposing mercury in fish does not mean you oppose fish,” Martin Kulldorff, the new ACIP chair, said in his opening remarks to the first meeting of the committee’s new members. The same is true for thimerosal, the uncommonly used preservative that contains a mercury atom but is safe for human use, including as a vaccine additive. ACIP surprised many by putting thimerosal’s use in influenza vaccines—of which 94% don’t contain the preservative—up to a vote. Thimerosal was removed from most other vaccines 25 years ago.

If public trust in one airline falls, it falls for all airlines, Kulldorff added, contending that the same holds true for vaccines.

At its first meeting, a few members of the new ACIP committee kicked things off by introducing themselves and discussing their potential conflicts of interest. Kulldorff and Robert Malone—both reported to have conflicts with Merck—disclosed no conflicts. Kulldorff said he used to work at Harvard but was fired for not getting a COVID-19 vaccine, choosing the “superior immunity” he said he obtained from a previous infection.

Vicky Pebsworth, a nurse with a doctorate in public health, said her stock holdings in healthcare companies and vaccine manufacturers were below what she claimed was the maximum allowable amount and therefore she was allowed to participate in the meeting. After Cody Meissner, a professor of pediatrics at the Geisel School of Medicine at Dartmouth, introduced himself, technical issues precluded the other three members from doing so.