The national immunization program : hearing of the Committee on Health, Education, Labor, and Pensions, United States Senate, One Hundred Seventh Congress, first session on examining the national immunization program, focusing on the importance of strengthening the public health system to detect and respond to bioterrorist attacks, produce an adequate supply of vaccinations, and improve the developments of counter-measures against other types of bioterrorist attacks, November 27, 2001.