A law went into effect on April 1, 2006 that changed the amount of mercury allowed in vaccines for certain groups.
After April 1, it is illegal for children under three and knowingly pregnant women to receive vaccines with more than a trace amount of mercury (one microgram of mercury per 0.5 milliliter dose, according to the FDA).
The mercury found in some multi-dose vials of vaccine is commonly called “thimerosal,” and is used as a preservative for the vaccine. In the 1990s, thimerosal was removed from all vaccines, except for multi-dose vials of influenza and Td.
Within the Vaccines for Children Program, the only vaccines containing thimerosal are: