Obama, though excited, was not yet prepared to order military action. John Brennan, Obama’s counterterrorism adviser, told me that the President’s advisers began an “interrogation of the data, to see if, by that interrogation, you’re going to disprove the theory that bin Laden was there.” The C.I.A. intensified its intelligence-collection efforts, and, according to a recent report in the Guardian, a physician working for the agency conducted an immunization drive in Abbottabad, in the hope of acquiring DNA samples from bin Laden’s children. (No one in the compound ultimately received any immunizations.)

Nicholas Schmidle, “Getting Bin Ladin”