Risk of Guillain–Barré syndrome following pandemic influenza A(H1N1) 2009 vaccination in Germany

Abstract

PurposeA prospective, epidemiologic study was conducted to assess whether the 2009 pandemic influenza A(H1N1) vaccination in Germany almost exclusively using an AS03-adjuvanted vaccine (Pandemrix) impacts the risk of Guillain–Barré syndrome (GBS) and its variant Fisher syndrome (FS).MethodsPotential cases of GBS/FS were reported by 351 participating hospitals throughout Germany. The self-controlled case series methodology was applied to all GBS/FS cases fulfilling the Brighton Collaboration (BC) case definition (levels 1–3 of diagnostic certainty) with symptom onset between 1 November 2009 and 30 September 2010 reported until end of December 2010.ResultsOut of 676 GBS/FS reports, in 30 cases, GBS/FS (BC levels 1–3) occurred within 150 days following influenza A(H1N1) vaccination. The relative incidence of GBS/FS within the primary risk period (days 5–42 post-vaccination) compared with the control period (days 43–150 post-vaccination) was 4.65 (95%CI [2.17, 9.98]). Similar results were found when stratifying for infections within 3 weeks prior to onset of GBS/FS and when excluding cases with additional seasonal influenza vaccination. The overall result of temporally adjusted analyses supported the primary finding of an increased relative incidence of GBS/FS following influenza A(H1N1) vaccination.ConclusionsThe results indicate an increased risk of GBS/FS in temporal association with pandemic influenza A(H1N1) vaccination in Germany. © 2014 The Authors. Pharmacoepidemiology and Drug Safety published by John Wiley & Sons, Ltd.

Pandemic influenza A vaccination and incidence of Guillain–Barré syndrome in Korea

“…However, other studies reported increased rates of GBS during pandemic periods [5,7]. Indeed, a few studies have even found a small but significant increase in the GBS incidence rate after pH1N1 vaccination [8][9][10][11]28,29]. Vaccination for pH1N1 appears to be accompanied by 0.74-2 additional GBS cases per million doses, which are similar to studies of the seasonal influenza vaccine [8,11,30].…”

Risk of Guillain-Barré syndrome after exposure to pandemic influenza A(H1N1)pdm09 vaccination or infection: a Norwegian population-based cohort study

“…A Canadian study showed a small but significant increase in the number of GBS cases after mass influenza vaccination in Quebec [21] and a study from Germany on the Pandemrix vaccine reported a statistically significant association between GBS and vaccination in a 5-42 days risk window [6]. Unlike other studies, an American study by Vellozzi et al [22] suggested a protective effect of influenza A (H1N1) vaccination.…”

“…While some studies show a lack of association between GBS following influenza A (H1N1) vaccination [3,8,9,14,20], an increased risk of GBS following pandemic vaccination has been reported in other studies [5,6,21,22]. Many of these studies, however, did not address influenza infection as a risk factor for GBS.…”

“…Also, after the influenza A(H1N1)pmd09 pandemic in 2009, have several studies reported an association between H1N1 immunizations and GBS [5][6][7], while other studies have not found any association [3,8,9]. Thus the role of vaccination as a possible trigger of GBS is unclear.…”

“…Previous studies on GBS following the 2009 pandemic were mainly based on case-centre designs (collaborations between various health centres) [3], records collected from selected hospitals [6,20,21], or a case-control design [14]. These studies are therefore prone to biases from selection of participants, the methods of collecting information and recall bias.…”