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

The World Health Organization (WHO) has affirmed that there is no evidence indicating any harm associated with the vaccine ingredient thimerosal, which has recently faced opposition from a newly established US medical panel.

During a press briefing, Kate O'Brien, the WHO's vaccine chief, emphasized that thimerosal is safe for use, countering claims made by the panel, appointed by US Health Secretary Robert F. Kennedy Jr., which voted against the longstanding recommendations for vaccines containing this preservative. The panel's decision is rooted in the false narrative propagated by the anti-vaccine movement linking thimerosal to autism.

Thimerosal is a preservative used to prevent bacterial and fungal contamination in multi-dose vials. It has undergone extensive study, and health authorities have consistently found no evidence of harm associated with its use, aside from minor reactions at the injection site. Although 96% of influenza vaccines administered in the United States during the 2024-2025 season did not contain thimerosal, it remains a crucial component in lower-income countries where multi-dose vials are more common. These vials require repeated puncturing, which increases the risk of contamination.

Thimerosal contains ethylmercury, an artificial form of mercury that is eliminated from the body much more rapidly than its natural counterpart. In response to safety concerns, US manufacturers voluntarily removed thimerosal from most pediatric vaccines in 2001. O'Brien highlighted its significance, stating that this ingredient is essential to ensure the availability of vaccines that protect children from serious and potentially life-threatening diseases.

She further explained that while extensive efforts have been made to eliminate thimerosal from vaccines out of an abundance of caution, it is vital for the public to understand that thorough reviews have confirmed the safety of this ingredient. O'Brien reiterated that some vaccines still require thimerosal to meet the necessary supply demands.

The recent recommendations from the Advisory Committee on Immunization Practices (ACIP) have raised concerns among experts, who fear that such decisions may lend support to anti-vaccine rhetoric and influence national health policy. This follows the abrupt dismissal of all 17 ACIP members by Kennedy, who alleged conflicts of interest without substantiating evidence.

The new panel has recommended the removal of thimerosal from influenza vaccines for children, pregnant women, and eventually for all adults, a move that has sparked alarm within the public health community.