Montgomery County does not offer Thimerosal-free flu vaccine. Thimerosal has a proven track record of being very safe. Data from many studies show no convincing evidence of harm caused by the low doses of Thimerosal in vaccines. However, children flu vaccines (6months - 18 years of age) are single doses, pre-filled syringes, 0.5 ml and thimerosol-free (no preservative).