No serological evidence of influenza A H1N1pdm09 virus infection as a contributing factor in childhood narcolepsy after Pandemrix vaccination campaign in Finland

PLoS One. 2013 Aug 8;8(8):e68402. doi: 10.1371/journal.pone.0068402. eCollection 2013.


Background: Narcolepsy cataplexy syndrome, characterised by excessive daytime sleepiness and cataplexy, is strongly associated with a genetic marker, human leukocyte antigen (HLA) DQB1*06:02. A sudden increase in the incidence of childhood narcolepsy was observed after vaccination with AS03-adjuvanted Pandemrix influenza vaccine in Finland at the beginning of 2010. Here, we analysed whether the coinciding influenza A H1N1pdm pandemic contributed, together with the Pandemrix vaccination, to the increased incidence of childhood narcolepsy in 2010. The analysis was based on the presence or absence of antibody response against non-structural protein 1 (NS1) from H1N1pdm09 virus, which was not a component of Pandemrix vaccine.

Methods: Non-structural (NS) 1 proteins from recombinant influenza A/Udorn/72 (H3N2) and influenza A/Finland/554/09 (H1N1pdm09) viruses were purified and used in Western blot analysis to determine specific antibody responses in human sera. The sera were obtained from 45 patients who fell ill with narcolepsy after vaccination with AS03-adjuvanted Pandemrix at the end of 2009, and from controls.

Findings: Based on quantitative Western blot analysis, only two of the 45 (4.4%) Pandemrix-vaccinated narcoleptic patients showed specific antibody response against the NS1 protein from the H1N1pdm09 virus, indicating past infection with the H1N1pdm09 virus. Instead, paired serum samples from patients, who suffered from a laboratory confirmed H1N1pdm09 infection, showed high levels or diagnostic rises (96%) in H1N1pdm virus NS1-specific antibodies and very high cross-reactivity to H3N2 subtype influenza A virus NS1 protein.

Conclusion: Based on our findings, it is unlikely that H1N1pdm09 virus infection contributed to a sudden increase in the incidence of childhood narcolepsy observed in Finland in 2010 after AS03-adjuvanted Pandemrix vaccination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Antibody Formation
  • Child
  • Child, Preschool
  • Finland / epidemiology
  • Humans
  • Influenza A Virus, H1N1 Subtype / immunology*
  • Influenza A Virus, H3N2 Subtype / immunology
  • Influenza Vaccines / adverse effects*
  • Influenza Vaccines / therapeutic use*
  • Influenza, Human / complications*
  • Influenza, Human / epidemiology
  • Influenza, Human / immunology*
  • Influenza, Human / prevention & control
  • Narcolepsy / etiology*
  • Pandemics
  • Serologic Tests
  • Viral Nonstructural Proteins / immunology


  • Influenza Vaccines
  • Viral Nonstructural Proteins
  • pandemrix

Grants and funding

This study was supported by the Medical Research Council of the Academy of Finland (grants 252252, 260603 and 261014), the Sigrid Juselius Foundation and Ministry of Social Affairs and Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.