evidence: Thimerosal was removed from all childhood vaccines in 2001 with the exception of inactivated flu vaccine in multi-dose vials. However, thimerosal has been removed from all single-dose preparations of flu vaccine for children and adults. No acceptable alternative preservative has yet been identified for multi-dose flu vaccine vials. [...] Why is thimerosal still in some flu vaccines that children may receive? [...] The childhood vaccines that used to contain thimerosal as a preservative are now put into single-dose vials or syringes, so no preservative is needed. In the past, these vaccines were put into multi-dose vials, which could become contaminated when new needles were used to get vaccine out of the vial for each dose.