Five cases of GBS were reported soon after the vaccine was administered. Although America's drugs regulator, the Food and Drug Administration (FDA), says it is not certain that the vaccine has caused the outbreaks, it considers it its public duty to alert people to the possibility because of its "potentially serious nature". FDA officials are actively investigating the link.
GBS can suddenly appear in healthy individuals or after an infection. It causes severe weakness in the arms and legs that can even lead to a paralysis in which the sufferer is unable to breathe. This is life-threatening, of course, and requires emergency hospital treatment. It can take up to three years to fully recover. The FDA is urging all Americans to report any suspected cases of GBS to the Vaccine Adverse Event Reporting System.