From the Centers for Disease Control: "Guillain-Barré syndrome (GBS) is a rare disorder in which a person’s own immune system damages their nerve cells, causing muscle weakness and sometimes paralysis. ... About two-thirds of people who develop GBS symptoms do so several days or weeks after they have been sick .... On very rare occasions, they may develop GBS in the days or weeks after getting a vaccination. GBS can cause symptoms that usually last for a few weeks. Most people recover fully from GBS, but some people have long-term nerve damage. In very rare cases, people have died of GBS, usually from difficulty breathing. In the United States ... an estimated 3,000 to 6,000 people develop GBS each year on average, whether or not they received a vaccination."