Which syndrome was associated with the 1976 U.S. swine-flu vaccine recall?

The 1976 U.S. swine-flu vaccine program was halted after an increased risk of Guillain–Barré syndrome was identified.

The campaign began after a novel influenza strain was detected at Fort Dix, New Jersey, and officials feared a repeat of the deadly 1918 pandemic. About 45 million Americans were vaccinated before the program was suspended. Investigators estimated that the vaccine was associated with roughly one additional Guillain–Barré case per 100,000 recipients.

Guillain–Barré syndrome is a rare disorder in which the immune system attacks peripheral nerves, causing weakness and sometimes paralysis. It is not the same as influenza, and the vaccine did not cause a nationwide swine-flu epidemic.

The episode became an important case study in risk communication, vaccine surveillance, and public-health decision-making. The feared pandemic did not develop, while the vaccine-associated neurological risk led authorities to stop the campaign.