The Ghost Study

How Thimerosal Conspiracies Keep Resurfacing

The Ghost Study: How Thimerosal Conspiracies Keep Resurfacing

The conference room at the Centers for Disease Control was designed for serious deliberation, the kind of place where careful people make careful decisions about protecting public health. But on June 24, something unusual happened in that space. During a presentation to the CDC's Advisory Committee on Immunization Practices (ACIP), Lyn Redwood of Children's Health Defense cited a 2008 study in Neurotoxicology by "Berman RF, et al" that supposedly showed "long-term consequences in the brain" from thimerosal exposure in newborn rats.

"There is no such paper," Dr. Robert F. Berman told CNN, adding he was "concerned and displeased" his name had been misused. Berman did publish a 2008 paper with a similar title, but it was in a different journal, involved different animals, and reached dramatically different conclusions. His actual research "did not find evidence of thimerosal exposure at vaccine levels" causing behavioral changes relevant to autism.

It was, in the most literal sense, a ghost citation: a scientific claim that materialized from thin air, presented in a forum designed to inform national vaccine policy. The CDC quietly removed the citation from Redwood's presentation later that day.

Today, ACIP reconvenes for another meeting on the same topic. The agenda includes renewed calls for the complete removal of thimerosal from all vaccines, including the multi-dose flu shots that still contain it. The arguments will be familiar: that thimerosal is ineffective as a preservative, that unused flu vaccines must be disposed of as "hazardous waste," and that pregnant women receiving these vaccines are exposing their unborn children to dangerous mercury.

None of these arguments are new. All have been thoroughly examined and found wanting. Yet here they are again, seeking an audience with the very people responsible for protecting Americans from preventable disease. It's a case study in how conspiracy theories evolve not by finding new evidence, but by finding new venues.

What Thimerosal Actually Is

Since the 1930s, thimerosal has served a simple but critical function: preventing contamination by bacteria and fungi in multi-dose vaccine vials. When a vial is punctured repeatedly to draw individual doses, each entry creates a potential pathway for microorganisms. Without preservatives, those repeated punctures pose real risks. History offers a tragic lesson: in 1928, a typhoid vaccine in Australia, packaged without preservative, became contaminated with staph and twelve children died.

The chemistry here matters enormously. Thimerosal is approximately 49.6 percent mercury by weight, but it contains ethylmercury, which is often confused with methylmercury (the form found in certain fish). These are fundamentally different compounds. In infant macaques, the blood half-life of ethylmercury was just two to nine days, versus twenty-two days for methylmercury, and brain concentrations were three-fold lower for the ethyl form (Burbacher et al., 2005). Ethylmercury is broken down and excreted rapidly; it doesn't accumulate like methylmercury does.

In 1997, the FDA assessed cumulative mercury exposure from all sources. At that time, a fully vaccinated six-month-old could receive up to 187.5 micrograms of ethylmercury, exceeding EPA guidelines designed for methylmercury exposure. As a precaution, health agencies recommended removing thimerosal from childhood vaccines in 1999 (CDC, 1999). By 2003, all routine pediatric vaccines were available thimerosal-free.

Today, the only U.S. vaccines that still use thimerosal as a preservative are some multi-dose influenza vials, primarily used in settings where speed, cost, or supply chain flexibility matter. Each 0.5 milliliter flu shot contains 25 micrograms of ethylmercury. The CDC confirmed that about 96 percent of flu shots are now thimerosal-free.

Crucially, thimerosal was removed as a precaution, not because it was proven dangerous.

Debunking Tomorrow's Arguments

The "Toxic Waste" Claim: Speakers will argue that flu vaccine vials must be disposed of as hazardous waste because they exceed EPA mercury limits. This sounds alarming until you understand the science. The EPA's rule tests what happens if substances leach from landfills into groundwater. A 0.5 milliliter flu shot contains 25 micrograms of mercury—one five-hundred-thousandth of a liter. By the same EPA standard, a tuna sandwich or broken fluorescent bulb would also qualify as "hazardous waste." Toxicity depends on actual dose, not concentration in landfill scenarios.

The "Ineffective Preservative" Claim: Critics will cite historical contamination incidents, including a 1985 outbreak where vaccine vials became contaminated despite containing thimerosal. But the study's authors concluded that preservatives work when proper sterile technique is used—no preservative can overcome gross contamination (Stetler et al., 1985). The U.S. Pharmacopeia requires 0.01 percent thimerosal to kill challenge microbes, and it passes (FDA guidance).

The Brain Mercury Claim: A 2005 primate study showed thimerosal-exposed monkeys had higher proportions of inorganic mercury in brain tissue compared to methylmercury-exposed monkeys. Critics omit crucial context: total mercury levels in the brain were actually much lower in the thimerosal group, and when scientists looked for behavioral harm, they found none (Burbacher et al., 2005). A controlled 2015 study found no autism-like behaviors in macaques receiving thimerosal-containing vaccines (Gadad et al., 2015).

The Autism Studies Are Clear

The claim that thimerosal causes autism has been tested exhaustively. Large population studies across multiple countries consistently find no link. Hviid and colleagues followed 537,303 Danish children and found no association between thimerosal exposure and autism (JAMA 2003). The U.S. Vaccine Safety Datalink study by Verstraeten and colleagues reached the same conclusion after analyzing data from hundreds of thousands of American children (Pediatrics 2003). Andrews and colleagues examined 109,863 British children and found no link (Pediatrics 2004). Price and colleagues specifically studied prenatal exposure and found no increased autism risk (Pediatrics 2010).

The Institute of Medicine reviewed more than 200 studies in 2004 and concluded that "the evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism" (IOM, 2004).

Most telling: if thimerosal caused autism, rates should have dropped after removal. They didn't. Denmark removed thimerosal in 1991 and autism rates rose. The U.S. completed removal by 2003, and autism rates continued climbing (Schechter & Grether, 2008).

Why This Still Matters

Today, about 96 percent of the U.S. flu vaccine supply is thimerosal-free (CDC). Only multi-dose vials contain it, for practical reasons: they can be filled months faster than individual syringes, cost roughly 50 percent less, and proved essential during the H1N1 pandemic when single-dose supplies ran short first.

Eliminating thimerosal would not make vaccines safer, but it would make them harder to deliver, especially to underserved communities. It would compromise pandemic preparedness and validate campaigns built on ghost studies. When international bodies considered banning thimerosal globally in 2012, the WHO and American Academy of Pediatrics opposed it, noting that "numerous studies have failed to find evidence of any harm from thimerosal in vaccines, and banning the preservative could adversely affect worldwide vaccine supply" (AAP statement, 2012). This stance explicitly recognized the equity implications: restricting access to affordable vaccines hurts the most vulnerable populations.

The Pattern of Misinformation

The ghost citation isn't an isolated incident. It represents a broader pattern where advocates cite phantom papers, misrepresent studies, and ignore evidence from millions of children. This isn't the first time reports connected to RFK Jr.'s health initiatives have included faulty citations; the Trump administration's Make America Healthy Again report also cited studies that don't exist, which an HHS spokesperson dismissed as "minor citation and formatting errors."

Misrepresentations like this aren't rare; they're a feature, not a bug. When questioned about these errors in a House hearing this week, Kennedy insisted that "all of the foundational assertions in that report are accurate" and said mistakes "were corrected within 24 hours." But when "evidence" relies on studies that don't exist while dismissing research from four countries involving millions of children, it's not science. It's misinformation dressed in scientific language.

The thimerosal controversy persists because it speaks to deeper anxieties about medical authority and parental autonomy. Parents facing autism diagnoses want explanations and accountability. The scientific answer (that autism appears largely genetic with complex, partially unknown causes) can feel unsatisfying. Conspiracy theories offer clarity and villains.

The Bottom Line

After two decades of research involving hundreds of thousands of children, the scientific consensus is clear. The FDA states that "a robust body of peer-reviewed studies supports the safety of thimerosal-containing vaccines." The CDC confirms: "There is no evidence of harm caused by the low doses of thimerosal in vaccines" (CDC vaccine safety).

Today's ACIP meeting will likely reaffirm this consensus. The real question isn't whether thimerosal is safe—the evidence is overwhelming that it is. The question is whether we'll continue allowing ghost studies and phantom citations to influence policy discussions about protecting public health.

As Dr. David Boulware, the infectious diseases professor who first flagged the nonexistent citation, noted: "The conclusion on that slide seemed really strong and definitive," prompting him to look up the research—only to discover it didn't exist (CNN, June 24, 2025).

Debates should be grounded in evidence, not speculation. And evidence that doesn't exist can't guide decisions that affect millions of lives.