Concern about the forthcoming vaccine is understandable and centers on the experience during the 1976-77 flu season. That's when a swine flu outbreak at Fort Dix, N.J., led the federal government to expedite vaccine production. Some 40 million people were vaccinated, including President Gerald R. Ford, by the time Guillain-Barre syndrome (GBS), a rare neurological disorder, was identified as a side effect.