• Dale R Burwen, Sukhminder K Sandhu, Thomas E MaCurdy, Jeffrey A Kelman, Jonathan M Gibbs, Bruno Garcia, Marianthi Markatou, Richard A Forshee, Hector S Izurieta, Robert Ball, and Safety Surveillance Working Group.
• Office of Biostatistics and Epidemiology, Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, MD, USA. dale.burwen@nih.gov
• Am J Public Health. 2012 Oct 1; 102 (10): 1921-7.

ObjectivesWe implemented active surveillance for Guillain-Barré syndrome (GBS) following seasonal or H1N1 influenza vaccination among the Medicare population during the 2009-2010 influenza season.MethodsWe used weekly Medicare claims data to monitor vaccinations and subsequent hospitalizations with principal diagnosis code for GBS within 42 days. Group sequential testing assessed whether the observed GBS rate exceeded a critical limit based on the expected rate from 5 previous years adjusted for claims delay. We evaluated the lag between date of service and date of claims availability and used it for adjustment.ResultsBy July 30, 2010 (after 26 interim surveillance tests), 14.0 million seasonal and 3.3 million H1N1 vaccinations had accrued. Taking into account claims delay appropriately lowered the critical limit during early monitoring. The observed GBS rate was below the critical limit throughout the surveillance.ConclusionsMedicare data contributed rapid safety monitoring among millions of 2009-2010 influenza vaccine recipients. Adjustment for claims delay facilitates early detection of potential safety issues. Although limited by lack of medical record review to confirm cases, this claims-based surveillance did not indicate a statistically significant elevated GBS rate following seasonal or H1N1 influenza vaccination.

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