You are not paying attention. The single-dose versions that were targeted at administration to children explicitly do not. The nasal inhalation version that was targeted for pregnant women explicitly does not. The multi-dose vials are the ones that contain Thimerosal, and those are explicitly NOT for pregnant women nor young children.
"Thimerosal, a mercury derivative, is not used in the manufacturing process for the single dose presentations; therefore these products contain no preservative. The multi-dose presentation contains thimerosal, added as a preservative; each 0.5 mL dose contains 24.5 mcg of mercury. " From: http://www.fda.gov/downloads/BiologicsBloodVaccines/Vaccines....