Montgomery County Dennis Avenue Health Center Immunization offers the Thimerosal-free (no preservative) adult flu vaccine (pre-filled single dose vials) and the multi-dose flu vaccine with Thimerosal. 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. All children flu vaccines (6months - 18 years of age) are single doses, pre-filled syringes, 0.5 ml and thimerosal-free (no preservative).