Background: In 2010, a safety signal was detected for narcolepsy following vaccination with Pandemrix, an AS03-adjuvanted monovalent pandemic H1N1 influenza (pH1N1) vaccine. To assess a possible association and inform policy on future use of adjuvants, we conducted a global study of narcolepsy and adjuvanted pH1N1 vaccines.
Methods: We used electronic health records for a dynamic retrospective cohort study to assess narcolepsy incidence rates (IR) before and during pH1N1 virus circulation, and after pH1N1 vaccination campaigns in Canada, Denmark, Spain, Sweden, Taiwan, the Netherlands, and United Kingdom. The case-control study evaluated the risk of narcolepsy following AS03- and MF59-adjuvanted pH1N1 vaccines in Argentina, Canada, Spain, Switzerland, Taiwan, and the Netherlands. In the Netherlands, we conducted a case-coverage study in children.
Findings: No changes in narcolepsy IRs were observed in any periods in any sites except Sweden and Taiwan; in Taiwan incidence increased after wild-type pH1N1 virus circulation and in Sweden (i.e., signaling country), incidence increased after the start of pH1N1 vaccination. No association was observed for Arepanrix-AS03 or Focetria-MF59 adjuvanted pH1N1 vaccines and narcolepsy in children or adults in the case-control study nor for children in the case-cover coverage study for Pandemrix-AS03.
Interpretation: Other than in Sweden, we did not find an association between receipt of AS03- or MF59-adjuvanted pH1N1 vaccines and narcolepsy in children or adults in the sites studied.
These results are in contrast to findings from other signaling Nordic countries (notably Finland and Norway) where an increased risk was observed following wild-type pH1N1 virus circulation and Pandemrix-AS03 vaccination.
Funding: This study was funded by the Centers for Disease Control and Prevention (CDC), Atlanta, USA, under CDC contract number 200-2012-53425_addendum 0001.