Guillain-Barre Syndrome

GBS is rare.

Anyone can develop GBS; however, it is more common among older adults. The rate of GBS increases with age, and people older than 50 years are at greatest risk for developing GBS. Each year, between 3,000 and 6,000 people in the United States get GBS, regardless of vaccination. To study whether a new vaccine might be causing GBS, CDC would compare this usual rate of GBS to the observed rate of GBS while the new vaccine was being given.  This helps to determine whether a vaccine could be causing more cases.

GBS may have several causes.

While it is not known what causes all cases of GBS, it is known that about two-thirds of people who get GBS do so several days or weeks after they have been sick with diarrhea or a lung or sinus illness. Infection with the bacteria Campylobacter jejuni is one of the most common risk factors for GBS. People also can develop GBS after having the flu or other infections such as cytomegalovirus and Epstein Barr virus. On very rare occasions, people develop GBS in the days or weeks after getting a vaccination.

In 1976 there was a small increased risk of GBS after swine flu vaccination.

The Institute of Medicine (IOM) conducted a scientific review of this issue in 2003 and found that people who received the 1976 swine influenza vaccine had an increased risk for developing GBS. The increased risk was approximately one additional case of GBS for every 100,000 people who got the swine flu vaccine. Scientists have several theories about the cause, but the exact reason for this link remains unknown.

The link between GBS and flu vaccination in other years is unclear, and if there is any risk for GBS after seasonal flu vaccines it is very small, about one in a million.  Studies suggest that it is more likely that a person will get GBS after getting the flu than after vaccination.  It is important to keep in mind that severe illness and death are associated with flu, and getting vaccinated is the best way to prevent flu infection and its complications.

Vaccine safety monitoring systems are used to investigate cases of GBS that start after vaccination.

Tracking vaccine safety is a high priority for CDC. Several systems are in place to monitor vaccine safety. One of these systems is the Vaccine Adverse Event Reporting System (VAERS).

CDC and the U.S. Food and Drug Administration (FDA) co-manage VAERS, which serves as an early warning system to collect voluntary reports about possible health problems that people experience following vaccinations. Anyone can report a suspected health problem after vaccination to VAERS.  CDC and FDA scientists regularly review all reports to detect new, unusual, or rare health events that could be linked to vaccines.

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