WHO Confirms No Evidence of Harm from Vaccine Ingredient Opposed by US Panel

On June 27, 2025, the World Health Organization (WHO) announced that there is no evidence suggesting that the preservative thimerosal, used in some vaccines, causes harm to health. This statement comes amid recent developments where a US medical panel, appointed by Health Secretary Robert F. Kennedy Jr., voted to oppose longstanding recommendations supporting the use of vaccines containing thimerosal. The US panel's decision has sparked controversy, especially among anti-vaccine groups, despite extensive scientific evidence demonstrating the safety of thimerosal.

WHO vaccine chief Kate O’Brien clarified during a press conference that "there is no evidence of harm from the use of thimerosal," addressing concerns raised by the US panel's recent stance. She emphasized that thimerosal, which contains ethylmercury, has been thoroughly studied and found safe, with most concerns about it being based on false links to autism. In fact, in the 2024-2025 flu season, about 96% of US flu vaccines did not contain thimerosal, but it remains crucial in many lower-income countries where multi-dose vials are common, and the risk of bacterial contamination is higher.

Thimerosal has been phased out of most pediatric vaccines in the US since 2001, but it is still used in some vaccines because of its preservative properties. It helps prevent bacterial and fungal growth in multi-dose vials, ensuring vaccine safety during storage and administration. The preservative contains ethylmercury, which is processed and eliminated from the body more quickly than other types of mercury, posing minimal health risks.

The recent voting by the US panel has raised concerns among health experts, as it could be seen as influenced by anti-vaccine rhetoric. Kennedy's decision to dismiss all 17 members of the Advisory Committee on Immunization Practices (ACIP) has further fueled debates, especially as the new panel recommended removing thimerosal from influenza vaccines for children, pregnant women, and adults.

WHO maintains that a comprehensive review of existing data confirms the safety of thimerosal, underscoring its importance in maintaining global vaccine supplies. Ensuring widespread immunization, particularly in resource-limited settings, depends on such preservatives to deliver safe and effective vaccines.

For more information, see the full report at Medical Xpress.