The 1976 swine flu outbreak, also known as the swine flu fiasco, or the swine flu debacle, was a strain of H1N1 influenza virus that appeared in 1976. Infections were only detected from January 19 to February 9, and were not found outside Fort Dix. The outbreak is most remembered for the mass immunization that it prompted in the United States. The strain itself killed one person and hospitalized 13. However, side-effects from the vaccine are thought to have caused five hundred cases of Guillain–Barré syndrome and 25 deaths.
However, allegedly this has been recently revisited and contested. For example:
Whether or not any of the antecedents had a causal relationship to GBS was, and remains, unclear. When cases of GBS were identified among recipients of the swine flu vaccines, they were, of course, well covered by the press. Because GBS cases are always present in the population, the necessary public health questions concerning the cases among vaccine recipients were "Is the number of cases of GBS among vaccine recipients higher than would be expected? And if so, are the increased cases the result of increased surveillance or a true increase?" Leading epidemiologists debated these points, but the consensus, based on the intensified surveillance for GBS (and other conditions) in recipients of the vaccines, was that the number of cases of GBS appeared to be an excess.
source: "Reflections on the 1976 Swine Flu Vaccination Program" in Emerging Infectious Diseases journal.
Although Wikipedia provides some references, to prevent getting an answer that simply repeats them, let me clarify that I am not happy with them because they are press articles, rather than peer reviewed papers.