It's been a mystery in Washington for weeks. Just before President Bush signed the homeland security bill into law an unknown member of Congress inserted a provision into the legislation that blocks lawsuits against the maker of a controversial vaccine preservative called thimerosal," used in vaccines that are given to children. Drug giant Eli Lilly and Company makes thimerosal. It's the mercury in the preservative that many parents say causes autism in thousands of children. But nobody in Congress would admit to adding the provision, reports CBS News Correspondent Jim Acosta - until now. House Majority Leader Dick Armey tells CBS News he did it to keep vaccine-makers from going out of business under the weight of mounting lawsuits. "I did it and I'm proud of it," says Armey, R-Texas. "It's a matter of national security," Armey says. Because Armey is retiring at the end of the year, some say the outgoing majority leader is the perfect fall guy to take the heat and shield the White House from embarrassment.