Pups were injected on post-natal days 7, 9, 11, and 15 with: vehicle, 1 × thimerosal (cumulative dose = 39.8 μg Hg/kg representing the maximum Hg exposure, on a μg/kg basis, to which a child could have been exposed from vaccination if hepatitis B, diphtheria tetanus pertussis (DPT), and Hemophilus influenza B (HiB) were conserved with thimerosal) or 10 × thimerosal (10-fold higher cumulative dose: 390 μg/kg). The gene discussed is DPT; the disease is Hepatitis.