The Trump administration's vaccine advisers are bringing up an old flu-shot debate: Whether it's time to wipe out the last small fraction of those vaccines that contain a controversial preservative.

A new slate of vaccine advisers to the US Centers for Disease Control and Prevention voted Thursday to recommend that Americans receive influenza vaccines that are free of thimerosal even though there is no evidence of harm from the preservative.

A CDC advisory panel voted 5–1 to recommend only flu vaccines without the preservative thimerosal, a mercury-containing compound used as a preservative in vaccines and other drugs. Doctors and physician advocacy groups warn that the decision could fuel vaccine hesitancy.