A team of independent researchers conducted a two-phase study: in Phase 1, examining Vaccine Adverse Event Reporting Systems (VAERS) data to compare ASD risk from DTaP vaccines with and without thimerosal; and in Phase 2 using VSD data to assess the likelihood of exposure of ASD cases to thimerosal-containing hepatitis B vaccines. In Phase 1, they found that ASD cases reported to VAERS from 1998-2000 were 2 times more likely to have had thimerosal-containing DTaP vaccines than thimerosal-free. In Phase 2, they found that ASD cases in the VSD database were 2.1 to 3.4 times more likely to have received thimerosal-containing hepatitis B vaccines than no hepatitis B vaccines. The authors concluded their analysis “provides new epidemiological evidence supporting an association between increasing organic-Hg exposure from Thimerosal-containing childhood vaccines and the subsequent risk of ASD diagnosis.”