WASHINGTON — Anti-vaccination activists, some with their (presumably unvaccinated) children, packed the Dirksen Senate Office Building Tuesday morning for a hearing that they hoped would vindicate, or at least recognize as legitimate, their fear that protecting their families from measles runs the risk of something worse, including autism and other disorders. As the doors closed on the room where the Senate Committee on Health, Education, Labor and Pensions was meeting, a woman could be heard pleading to be allowed in to give her side of what has become a heated, and potentially dangerous, controversy. That hope would be quickly dashed....