cience 3 January 1997: Vol. 275. no. 5296, pp. 40 - 41 DOI: 10.1126/science.275.5296.40 PERSPECTIVES Pax Polio Harry F. Hull The author is with the Global Programme for Vaccines and Immunization, World Health Organization, CH-1211 Geneva 27, Switzerland. Our dictionary defines millennium both as a period of a thousand years and as "a hoped