A preservative-free flu shot is a type of flu vaccine that does not contain the antimicrobial agent known as thimerosal. Thimerosal, a mercury-based compound, is an ingredient that's used in some ...

thimerosal, in flu vaccines and other shots given to children and pregnant women. The move was made in response to fears that thimerosal might cause neurological conditions such as autism.

Current flu shots are made from viruses grown in eggs ... Flublok does not contain any preservatives (e.g., thimerosal, a mercury derivative), antibiotics, egg proteins or latex.