Chart-Confirmed Guillain-Barre Syndrome After 2009 H1N1 Influenza Vaccination Among the Medicare Population, 2009-2010

Abstract

Given the increased risk of Guillain-Barré Syndrome (GBS) found with the 1976 swine influenza vaccine, both active surveillance and end-of-season analyses on chart-confirmed cases were performed across multiple US vaccine safety monitoring systems, including the Medicare system, to evaluate the association of GBS after 2009 monovalent H1N1 influenza vaccination. Medically reviewed cases consisted of H1N1-vaccinated Medicare beneficiaries who were hospitalized for GBS. These cases were then classified by using Brighton Collaboration diagnostic criteria. Thirty-one persons had Brighton level 1, 2, or 3 GBS or Fisher Syndrome, with symptom onset 1-119 days after vaccination. Self-controlled risk interval analyses estimated GBS risk within the 6-week period immediately following H1N1 vaccination compared with a later control period, with additional adjustment for seasonality. Our results showed an elevated risk of GBS with 2009 monovalent H1N1 vaccination (incidence rate ratio = 2.41, 95% confidence interval: 1.14, 5.11; attributable risk = 2.84 per million doses administered, 95% confidence interval: 0.21, 5.48). This observed risk was slightly higher than that seen with previous seasonal influenza vaccines; however, additional results that used a stricter case definition (Brighton level 1 or 2) were not statistically significant, and our ability to account for preceding respiratory/gastrointestinal illness was limited. Furthermore, the observed risk was substantially lower than that seen with the 1976 swine influenza vaccine.

The incidence and triggers of adult‐onset Guillain−Barré syndrome in southwestern Finland 2004–2013

“…Although an increased risk of GBS associated with the pandemic H1N1 influenza vaccine (Pandemrix) given during the 2009À2010 outbreak was found, this amounts to only one case. Previously, the vaccine has been associated with GBS in Germany [14] and weakly in the USA [15]. No association has been found in studies conducted in the UK [16] and in a European multinational case series [17] with one study from the USA reporting even a protective effect [18].…”

T cell epitope redundancy: cross-conservation of the TCR face between pathogens and self and its implications for vaccines and autoimmunity

“…There is also evidence of an association between influenza virus and GBS. In 1976 and 2009 in the US, seasonal influenza strains were of swine origin and an increased relative risk of developing GBS was observed in both cases, whether the vaccine was adjuvanted or not [72,73]. Although these results were not confirmed in Europe [74], several studies have established a link between GBS and infection by the 2009 pH1N1 [75,76].…”

A simulation study of the statistical power and signaling characteristics of an early season sequential test for influenza vaccine safety

“…Thus, we have complemented the use of USPRT with self‐controlled risk interval (SCRI) analyses, which provide less biased and more precise estimates of the GBS risk attributable to influenza vaccines by at least adjusting for time‐invariant confounders if not for time‐varying confounders such as influenza circulation . These two systems together with a descriptive analysis conducted during and after USPRT testing have constituted the active surveillance components of the FDA‐CMS multilayered surveillance system …”

“…Because USPRT depends on the accumulation of observed vaccinations { N 1 t , … , N tt } up to each testing week, we used data from the 2016 to 2017 influenza season in SSD to represent a hypothetical accumulation (Figure ). We used days 8 to 21 postvaccination as the risk window, where GBS risk attributable to vaccination is thought to be higher and 2.55 events per million vaccinations (the average rate in the seasons 2012‐2013 through 2016‐2017 among seasonal influenza vaccines) as the historical GBS rate . For the clinical delay distribution, we used the average distribution in the 2014 to 2015 through 2016 to 2017 seasons to reflect potential decreases in time needed to diagnosis GBS, whereas for the processing delay distribution, we used the 2016 to 2017 season only to reflect yearly decreases in the time elapsed for Medicare claims processing (Appendix S3).…”