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Critics of PubPeer, an online platform that allows anonymous comments on peer-reviewed articles, allege the platform is increasingly being used to target research that challenges mainstream views on vaccines and aluminum adjuvants.
After U.S. Health Secretary Robert F. Kennedy Jr. criticized a Danish study widely cited as proof of no association between aluminum-adjuvanted vaccines and chronic childhood disorders, two journals launched investigations into decade-old peer-reviewed papers suggesting a link.
French researcher Guillemette Crépeaux, Ph.D., was an author on both papers. Both journals cited anonymous PubPeer comments as the basis for their investigations.
Although one of the journals, Elsevier, ultimately closed its inquiry without taking action, a separate review by Frontiers in Neurology remains ongoing.
Danish study puts aluminum — and Crépeaux — in spotlight
In August 2025, Kennedy called for the retraction of the Danish study, describing it as “deeply flawed.”
In November 2025, advisers to the Centers for Disease Control and Prevention, who had formed a work group to study safety issues related to the childhood vaccine schedule, included aluminum adjuvants on their list of issues to examine.
This led to a discussion of aluminum safety during the December meeting of the Advisory Committee on Immunization Practices.
A few months later, Crépeaux, whose lab is among only a few worldwide to study aluminum adjuvant toxicity, learned that a paper her team published in Toxicology nearly a decade earlier was under investigation by Elsevier, the journal’s publisher.
In an email to Crépeaux, the journal cited “significant technical and ethical concerns raised on PubPeer.”
PubPeer is an online platform that allows users to publicly and anonymously critique scientific research after it has been published. Critics nicknamed it “PubSmear,” blaming it for driving a wave of retractions targeting peer-reviewed papers that challenge the mainstream narrative on vaccines, COVID-19 treatments and aluminum, among others.
Crépeaux told The Defender she thought her work was targeted because aluminum is receiving renewed attention, and because the papers challenge conventional thinking: that smaller amounts of toxic exposure are necessarily safer.
Crépeaux had also criticized the Danish study.
Aluminum toxicity expert Christopher Exley, Ph.D., and one of Crépeaux’s co-authors, said that publishers today are “heavily influenced by external forces.”
Anonymous complaint leads Elsevier to investigate decade-old study
In February 2026, Francesco Papi — “Publishing Ethics Expert at Elsevier” — contacted Crépeaux about a 2017 paper she and a group of co-authors published in Toxicology. The paper addressed safety issues with Alhydrogel, a widely used aluminum hydroxide gel adjuvant licensed for use in vaccines.
The study found that low — but not high — doses of Alhydrogel injected into mice’s muscles appeared to cause long-term aluminum accumulation in the brain with neurotoxic effects.
Crépeaux told The Defender their findings mattered, “because they directly challenge the simplistic ‘the lower the dose, the lower the toxicity’ argument that is frequently used to dismiss concerns about aluminium vaccine adjuvants.”
She said the particulate nature of aluminum-based adjuvants, which affects how cells absorb and process the adjuvants, “has yet to be adequately addressed in risk assessments or by official health authorities.”
In his email, Papi asked Crépeaux to respond to concerns raised on PubPeer alleging “potential data manipulation, research errors, and missing ethical approvals to this research.”
Papi’s email didn’t provide details, pointing instead to an anonymous 2018 PubPeer post containing spelling errors. He gave Crépeaux 14 days to respond.
“I’m deeply surprised that the Elsevier group stoops to consider pubpeer opinions and even asks respected researchers to answer that kind of comments!” Crépeaux replied.
She re-sent a response her team had published in Toxicology, rebutting a 2017 Letter to the Editor making similar claims — a letter the journal had run without first letting the authors respond, which the editors excused as “editorial oversight.”
In their published rebuttals, Crépeaux’s team called the allegations contained in the letter “erroneous.” She also noted that the letter’s authors, David Hawkes and Joanne Benhamu, were administrators of the pro-vaccine advocacy group Stop Australia’s (anti) Vaccine Network.
Elsevier closes case, but questions remain
Papi called that response insufficient. In further exchanges, Crépeaux repeatedly asked him to name the specific scientific issue in question. He continued citing the PubPeer thread generally and declined to identify who had filed the complaint.
“I would also like to note that the comments mentioned appear to date back approximately eight years, concerning an article published nine years ago. In addition, criticisms of this work have previously been raised publicly, and we responded to those points in a published Letter to the Editor,” Crépeaux wrote.
Papi then raised PubPeer claims of discrepancies between the published paper and an unnamed “preliminary report.” Crépeaux said she knew of no such report and asked for a citation. Elsevier described it only as “earlier publicly available material” referenced on PubPeer.
When Crépeaux asked again for “a precise and citable reference (document, date, source),” none was produced.
Unable to produce the report, on April 2, 2026, Papi told her the editor had reviewed the matter and closed the case with no further action.
But questions remained. In a Substack post on the issue, Exley, a co-author on the study, wrote that it was hard to understand “why a supposed legitimate publishing company such as Elsevier would be looking to address anonymous comments made eight years ago on a wholly corrupt website.”
Exley suggested someone with influence at Elsevier was pushing to have vaccine-related papers targeted and retracted. He said the team was “bracing ourselves for the next anonymous attack on our science and on our integrity.”
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Frontiers opens its own audit, again citing PubPeer
While the Elsevier investigation was ongoing, Crépeaux and colleagues learned that in February 2026, Frontiers in Neurology had opened a “post-publication research integrity audit” of a separate 2015 paper they’d co-authored on the effects of aluminum adjuvants on the brain.
Ann McGinley, “Research Integrity Auditor Specialist” at Frontiers, informed the authors that the audit followed “multiple concerns raised on the PubPeer platform.”
A comment published in 2018 suggested there may be the “perception” of a conflict of interest, because one author was funded by an adviser to an organization that also funded a Frontiers editor.
McGinley asked the authors to respond to detailed questions about possible conflicts of interest.
The paper was published over 10 years before the inquiry, but the “integrity concerns” were raised in 2026, while the Elsevier investigation was ongoing.
The authors didn’t receive the journal’s initial notices because they were sent to email addresses from over a decade prior.
In April 2026, Crépeaux, on behalf of the authors, provided a detailed response to the journal’s questions stating they had no conflicts of interest, that no funder influenced the study design and that all funding had been disclosed.
“In full transparency, you are not the first to contact us in recent weeks regarding PubPeer comments on articles that were published several years ago,” Crépeaux wrote.
“This situation has never occurred previously, which raises some concern on our side as to whether these inquiries may be driven by considerations that extend beyond strictly scientific discussion.”
She asked if a specific individual or entity had prompted the inquiry, noting that Elsevier had just closed its own case. The editors said their concerns were based solely on the PubPeer comments.
The authors are still awaiting the results of the inquiry.
The Research Integrity Office at Frontiers did not respond to The Defender’s request for comment on the case or on the broader role PubPeer plays in its decisions to review published, peer-reviewed articles.
Related articles in The Defender
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- ‘Vigilante Science’: How Anonymous Critics Are Trying to Silence Peer-Reviewed Vaccine Research
- Sen. Ron Johnson: There Used to Be ‘Serious Journalism’ on Vaccine Injuries — But COVID Vaccine Cancer Risks Still Being Suppressed
