Guillain-Barré Syndrome, 2009

Guillain-Barré syndrome (GBS) is an uncommon immune-mediated neurologic disorder causing limb weakness or numbness, ascending paralysis, and in severe cases respiratory failure and death. The estimated background rate of GBS is 1-2 cases per 100,000 people. The exact cause of GBS is unknown. It is often preceded by an antecedent illness such as gastrointestinal or respiratory infection, and rarely vaccinations.

In 2009, GBS was added to the Minnesota Rules Governing Communicable Diseases for a duration of 2 years. While not an infectious disease, it was added to aid post-licensure safety monitoring of the 2009 novel influenza A H1N1 vaccine. Enhanced surveillance was conducted October 1, 2009 through May 31, 2010.

In 1976, concerns about a possible large outbreak of a swine-origin influenza virus (influenza A/New Jersey/76 [Hsw1N1]; influenza A/NJ/76 (H1N1) virus), lead to a mass vaccination campaign in the United States. Epidemiologic studies showed a small, but significant, risk of GBS in adults vaccinated 6 to 8 weeks prior; the estimated risk was approximately 10 cases of GBS per 1 million vaccines. The increased risk, combined with the fact the influenza virus did not spread as expected, resulted in the termination of the vaccine program. Underlying reasons for the association between the 1976 vaccine and GBS remain unknown.

In 2009, the emergence of a novel pandemic swine-origin H1N1 influenza virus prompted rapid development of an influenza A (H1N1) 2009 vaccine. The association between GBS and the 1976 vaccine lead to theoretical concerns about a similar association existing with the 2009 vaccine. While the influenza A (H1N1) vaccine was anticipated to be as safe as the seasonal influenza vaccine, active post-licensure surveillance was initiated to rapidly identify all incident cases of GBS.

As part of EIP, Minnesota was one of 10 states which monitored the safety of the 2009 influenza A H1N1 vaccine. MDH established a network with all neurology clinics statewide that reported suspected GBS cases weekly. In addition, all hospital medical records departments screened discharge records biweekly to assure no GBS cases were missed. MDH reviewed medical records using a standardized case report form for each suspect GBS case. Information on antecedent infections and vaccination history, including influenza A H1N1 vaccine, in the 42 days prior to onset of GBS symptoms was collected. Case status was assigned according to Brighton clinical criteria.

As of December 31, 2009, MDH investigated 45 reports of possible GBS. Of these, 18 (40%) cases had confirmed GBS, 21 (47%) were non-cases, 5 (11%) were out of state residents, and 1 (2%) was still under investigation. MDH will continue to review medical charts in 2010 to identify incident cases. Nationally, CDC is evaluating whether there is an excess risk of GBS related to influenza A H1N1 vaccination; preliminary data showed a slightly increased risk of 0.8 excess cases per million vaccinees, no different than the excess risk associated with some seasonal influenza vaccines.

Updated Friday, November 19, 2010 at 03:16PM