The U.S. government has given an ultimatum to the international group that helps provide vaccines to children in the world's poorest countries.
In a statement sent to NPR, The Department of Health and Human Services said that Gavi, the Vaccine Alliance must remove the ingredient thimerosal from its vaccines — or else the U.S. will "withhold future new funding." The news was first reported by Reuters on Wednesday.
At the heart of the U.S. demand is an unsubstantiated theory that the mercury in thimerosal could be linked to autism. Thimerosal is a chemical compound that is added to vaccines as a preservative.
This is the latest development in the changing relationship between Gavi — which says it has provided vaccines for 1.1 billion children in lower-resource countries and prevented 18 million deaths — and the United States, once a major funder of the vaccine group.
In June, the Trump administration cut off more than a billion dollars previously promised to the group. At that time, HHS Secretary Robert F. Kennedy Jr. said that Gavi "ignores the science" when it comes to vaccine safety.
Now, thimerosal has become a new sticking point in the U.S.-Gavi relationship.
Although thimerosal has been used safely in medications and vaccines since the 1930s, it's also been the topic of a long-simmering debate that has reignited domestically in the past year. With this week's demand from HHS, the controversy is going global. And, experts say, the potential impact is substantially greater abroad than in the U.S. That's because this ingredient is critical for preventing contamination of vaccines in vials containing multiple doses that are often used in the Global South.
"The stakes are much higher in low-income countries," says Dr. William Moss, a professor at Johns Hopkins Bloomberg School of Public Health and executive director of the International Vaccine Access Center.
Here's more on the debate and the potential consequences.
Why and where is thimerosal used?
Thimerosal has a special antimicrobial property: It's very good at preventing the growth of bacteria and fungi. Thus, for decades, it's been added to vaccines to help avoid contamination.
This is particularly important for multiple-dose vials. For example, one bottle might contain 10 doses of the given vaccine. When a syringe goes into a vial to draw up the liquid, there is a risk of introducing germs. The presence of thimerosal deters growth of any germs.
In the U.S. the use of thimerosal has "significantly declined" — according to the FDA — partly because vaccines are now packaged in single-dose vials. Europe also relies heavily on single-dose vials.
However, in many places supported by Gavi, multi-dose vials are regularly used.
"High-income countries can afford single-dose vials, which are more expensive — and more expensive to transport and store," explains Moss. "But low-income countries have to maintain a cold chain and they just don't have the refrigerator space to be able to store the single-dose vials."
It's common for low-income countries to use multi-dose vials for immunization campaigns that last days or weeks, when a large number of children are vaccinated. "It's very efficient and cost effective to use these multi-dose vials as long as they don't get contaminated with bacteria or fungi — and that's exactly what the thimerosal is doing," says Moss.
Indeed, about 14% of Gavi's portfolio consists of vaccines that contain thimerosal in multi-dose vials, including the 5 in 1 pentavalent vaccine, the DTP vaccine that protects against diphtheria, tetanus and pertussis and the hepatitis B vaccine.
What's all the commotion about?
Thimerosal is about 50% mercury by weight.
That raises suspicions in some circles. "People think the T-1000, Terminator 2 — liquid metal that's going to cause serious brain injuries," says Angela Rasmussen, a virologist at the University of Saskatchewan and co-editor-in-chief of the scientific journal Vaccine.
In reality, she says, the type of mercury it contains is ethylmercury which quickly leaves the body and is not harmful in the amounts contained in vaccines. Methylmercury is a more dangerous type of mercury and can accumulate in the body when people are exposed in their environment or in certain foods, like fish.
"The dangerous mercury that could be toxic from a single thimerosal-containing vaccine is less than you would get from eating a tuna fish sandwich," she explains.
Leading health institutions agree with Rasmussen: Thimerosal has the blessing of the World Health Organization, whose advisory committee found "there is no evidence of toxicity in infants, children or adults exposed to thiomersal in vaccines."
Similarly, U.S. federal agencies have deemed it safe. The Centers for Disease Control and Prevention says on its website that "research does not show any link between thimerosal in vaccines and autism." And the Food and Drug Administration has found that "the scientific evidence collected over the past 20+ years does not show any evidence of harm."
However, HHS Secretary Kennedy disagrees.
And the State Department told NPR that RFK Jr. is calling the shots here. In a statement, it said: "President Trump has trusted Secretary Robert F. Kennedy Jr. to manage the U.S. Government's relationship with Gavi."
Kennedy has long campaigned against thimerosal. In 2014, he edited a book called Thimerosal: Let the Science Speak: The Evidence Supporting the Immediate Removal of Mercury – a Known Neurotoxin – from Vaccines. This summer, he said in a video that the mercury found in thimerosal is a "very potent neurotoxin," explaining his decision to order thimerosal removed from all influenza vaccines in the U.S.
However, the decision didn't have a huge impact because only about 6% of flu vaccines contained thimerosal.
Back in 2001, the U.S. removed thimerosal from nearly all vaccines routinely given to children under 6 as a precautionary measure. The American Academy of Pediatrics explains that this decision was made because all the misleading claims about thimerosal were "eroding public trust in vaccine safety," and it didn't want to risk children going without their shots.
The CDC website points out: "Even after thimerosal was removed from almost all childhood vaccines, autism rates continued to increase, which is the opposite of what would be expected if thimerosal caused autism."
The status of the ultimatum
The U.S is requesting from Gavi "a detailed action plan with a timeline for the phase-out of thimerosal-containing vaccines," according to a statement from HHS to NPR. The goal, the statement says, is to "bring the poorest countries in line with the standards in the U.S., Canada, [and] most European nations, who have long-since phased-out thimerosal-containing vaccines for children."
Gavi, in a statement to NPR, said: "We remain in contact on this subject," explaining that any change "would require a decision by Gavi's Board" and that it "will be guided by scientific consensus."
"It's extortion — essentially," the University of Saskatchewan's Rasmussen says of the Trump administration's demands to Gavi. "They're saying: Do Trump things. Do MAHAM things. Align yourself with our policies — in the absence of evidence — and we won't take all your money away."
Potential implications of the new U.S. demand
Gavi has not indicated that it would comply with the request. The HHS statement said, "Gavi has refused to develop this [phase-out] plan." Nonetheless, vaccine experts worry what could happen, if Gavi did agree to eliminate thimerosal from its vaccines.
It would make "vaccines more expensive in the developing world, which means that they will be available to fewer children," says Dr. Paul Offit, a pediatrician and director of the Vaccine Education Center at the Children's Hospital of Philadelphia. He says the ultimate outcome is clear: "Children will no doubt die because those vaccines are unavailable."
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