Risk of Confirmed Guillain-Barre Syndrome Following Receipt of Monovalent Inactivated Influenza A (H1N1) and Seasonal Influenza Vaccines in the Vaccine Safety Datalink Project, 2009-2010

Abstract

An increased risk of Guillain-Barré syndrome (GBS) following administration of the 1976 swine influenza vaccine led to a heightened focus on GBS when monovalent vaccines against a novel influenza A (H1N1) virus of swine origin were introduced in 2009. GBS cases following receipt of monovalent inactivated (MIV) and seasonal trivalent inactivated (TIV) influenza vaccines in the Vaccine Safety Datalink Project in 2009-2010 were identified in electronic data and confirmed by medical record review. Within 1-42 days following vaccination, 9 cases were confirmed in MIV recipients (1.48 million doses), and 8 cases were confirmed in TIV-only recipients who did not also receive MIV during 2009-2010 (1.72 million doses). Five cases following MIV and 1 case following TIV-only had an antecedent respiratory infection, a known GBS risk factor; furthermore, unlike TIV, MIV administration was concurrent with heightened influenza activity. In a self-controlled risk interval analysis comparing GBS onset within 1-42 days following MIV with GBS onset 43-127 days following MIV, the risk difference was 5.0 cases per million doses (95% confidence interval: 0.5, 9.5). No statistically significant increased GBS risk was found within 1-42 days following TIV-only vaccination versus 43-84 days following vaccination (risk difference = 1.1 cases per million doses, 95% confidence interval: -3.1, 5.4). Further evaluation to assess GBS risk following both vaccination and respiratory infection is warranted.

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].…”

“…After the first Korean pH1N1 case was identified on May 2, 2009, the Korea Centers for Disease Control and Prevention (KCDC) began a program of mass influenza vaccination on October 27, 2009. Although several studies have reported that pH1N1 vaccination is not associated with an increase in the risk of GBS, other epidemiologic studies have reported exactly the opposite [5][6][7][8][9][10][11][12]. However, these studies were limited by small GBS and pH1N1 vaccination sample sizes.…”

Prevention and Control of Seasonal Influenza with Vaccines

“…In addition, data from the systems monitoring influenza A(H1N1) 2009 monovalent vaccines suggest that the increased risk for GBS is approximately one or two additional cases per 1 million persons vaccinated, which is similar to that observed in some years for seasonal IIV (350)(351)(352)(353)(354)(355)(356). Studies have also shown an increased risk for GBS following influenza infection, of higher magnitude than the risk observed following influenza vaccination (338,357).…”

International collaboration to assess the risk of Guillain Barré Syndrome following Influenza A (H1N1) 2009 monovalent vaccines

“…This risk is consistent with the level of risk reported by others. Estimates from single-country studies ranged from 1.05 to 4.70, the majority of which reported statistically significant increased risk [23][24][25][26][27][28][29][30][31][32]. Estimates were lower in studies of adjuvanted vaccines (1.05-3.04) [25,31] than in non-adjuvanted vaccines (1.57-4.70) [26][27][28][29][30]32].…”