Oceans and armed might may protect nations from invading armies; nothing stops influenza. In 1918, the disease made a globe-girdling march that left 30 million dead. Modern outbreaks, though less horrendous, still pose a major public health threat. The 1968 epidemic affected more than 30 million in the U.S. alone, causing widespread school and job absenteeism and killing more than 200.
Because flu tends to erupt at ten-year intervals, doctors have been searching for a defense against the major epidemic expected to occur toward the end of the decade. Now they appear on the verge of success. Scientists at the National Institutes...