Background: The global spread of the 2009 novel pandemic influenza A (H1N1) virus led to the accelerated production and distribution of monovalent 2009 Influenza A (H1N1) vaccines (pH1N1). This pandemic provided the opportunity to evaluate the risk of Guillain-Barré syndrome (GBS), which has been an influenza vaccine safety concern since the swine flu pandemic of 1976, using a common protocol among high and middle-income countries. The primary objective of this project was to demonstrate the feasibility and utility of global collaboration in the assessment of vaccine safety, including countries both with and without an established infrastructure for vaccine active safety surveillance. A second objective, included a priori, was to assess the risk of GBS following pH1N1 vaccination.
Methods: The primary analysis used the self-controlled case series (SCCS) design to estimate the relative incidence (RI) of GBS in the 42 days following vaccination with pH1N1 vaccine in a pooled analysis across databases and in analysis using a meta-analytic approach.
Results: We found a relative incidence of GBS of 2.42 (95% CI 1.58-3.72) in the 42 days following exposure to pH1N1 vaccine in analysis of pooled data and 2.09 (95% CI 1.28-3.42) using the meta-analytic approach.
Conclusions: This study demonstrates that international collaboration to evaluate serious outcomes using a common protocol is feasible. The significance and consistency of our findings support a conclusion of an association between 2009 H1N1 vaccination and GBS. Given the rarity of the event the relative incidence found does not provide evidence in contradiction to international recommendations for the continued use of influenza vaccines.
Keywords: Adjuvant; Adverse events following immunization (AEFI); CPRD; CSF; Clinical Practice Research Datalink; Department of Defense; Department of Veterans Affairs; DoD; GP; Guillain Barré Syndrome (GBS); ICPI; Integrated Primary Care Information Database; International; MCRI; Maccabi; Maccabi Health Maintenance Organization; Monovalent H1N1 Vaccine (H1N1); Murdoch Children's Research Institute; NNI/CGH; NNI/TTSH; National Neuroscience Institute Singapore General Hospital; National Neuroscience Institute Tan Tock Seng Hospital; PRISM; Post-Licensure Rapid Immunization Safety Monitoring; Self-controlled case-series method (SCCS); VA; VAESCO; VSD; Vaccine Adverse Event Surveillance and Communication Consortium; Vaccine Safety Datalink; cerebrospinal fluid; general practitioner.
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