The Trump administration has told global vaccine group Gavi to phase out shots containing the preservative thimerosal as a condition of providing the group with funding, a US official and a Gavi spokesperson told Reuters.

The request, which Reuters is the first to report, is the latest sign of efforts by the administration of President Donald Trump to influence health policy globally.

Anti-vaccine groups, including one founded by US Health Secretary Robert F. Kennedy Jr., have for decades claimed that thimerosal, a mercury-based preservative used in vaccines, is linked to autism and other neurodevelopmental disorders, despite many studies showing no related safety issues.

In June last year, Kennedy cut $300 million in annual funding for Gavi, which helps the world's poorest and lower-income countries buy vaccines to prevent diseases such as measles and diphtheria.

Kennedy, who has long promoted anti-vaccine views contrary to scientific evidence, says the group ignores safety issues with the immunizations it provides. Gavi says vaccine safety is its utmost concern.

“Until a plan for removal of thimerosal-containing vaccines is developed and the plan initiated, the United States will withhold future new funding,” an official for the US Department of Health and Human Services told Reuters.

The official would not comment on when the request was made, but claimed Gavi has so far refused to develop such a plan. A Gavi spokesperson confirmed the request to remove thimerosal from its portfolio, and said the group remained in contact with the US government on the subject.

"While we very much hope to find a pathway to welcoming the U.S. back as a donor, any decision related to Gavi’s portfolio would require a decision by Gavi’s board and input from preceding governance committees, which will be guided by scientific consensus," the spokesperson said.

OFTEN USED IN LOW- AND MIDDLE-INCOME COUNTRIES

Thimerosal is mainly used to ensure vaccines in multi-dose vials remain stable. That helps immunization campaigns in low- and middle-income countries because multi-dose vials are cheaper and simpler to distribute, Gavi and the World Health Organization say.

The preservative has largely been phased out in high-income countries, where vaccines usually come in a single-use format, although its use is not prohibited. Under Kennedy, the US moved last summer to stop use of influenza vaccines containing thimerosal, representing around 5% of flu shots given in the country, despite US health agencies having declared them safe.

The US official said the request of Gavi aims to bring its policies in low- and middle-income countries in line with the US, Canada, and most European nations.

The safety of thimerosal has been studied for decades, after concerns were raised in the 1990s about exposure to mercury in vaccines, according to the WHO.

No compelling scientific evidence has been found to suggest that there is a risk, particularly when compared to the dangers of keeping children unprotected against deadly diseases, the WHO says.

The US request applies both to the remaining $300 million that the Biden administration had pledged to Gavi with Congressional approval, but which is still outstanding, and to any future funding, the official said.

The US previously contributed around 13% of Gavi’s funding, and the organization has embarked on a series of cost-cutting measures to try to address the shortfall, which has been exacerbated by cuts from other high-income nations.

The Trump administration has cut billions of dollars in health funding internationally and withdrawn from the WHO.

The US government has said it is still committed to global health and is pursuing bilateral agreements with countries under Trump's ‘America First’ agenda.

Last week, the US health department said a hepatitis B vaccine study in Guinea Bissau would help inform global policy.

The study, funded by the US Centers for Disease Control and Prevention, is now undergoing further ethical review after international criticism.

The US CDC last month withdrew its longstanding recommendation that all newborns should get the hepatitis B vaccine, drawing a swift rebuke from vaccine experts.