The incidence of narcolepsy in Europe: Before, during, and after the influenza A(H1N1)pdm09 pandemic and vaccination campaigns

Leonoor Wijnans, Coralie Lecomte, Corinne de Vries, Daniel Weibel*, Cormac Sammon, Anders Hviid, Henrik Svanström, Ditte Mølgaard-Nielsen, Harald Heijbel, Lisen Arnheim Dahlström, Jonas Hallgren, Par Sparen, Poul Jennum, Mees Mosseveld, Martijn Schuemie, Nicoline van der Maas, Markku Partinen, Silvana Romio, Francesco Trotta, Carmela SantuccioAngelo Menna, Giuseppe Plazzi, Keivan Kaveh Moghadam, Salvatore Ferro, Gert Jan Lammers, Sebastiaan Overeem, Kari Johansen, Piotr Kramarz, Jan Bonhoeffer, Miriam C.J.M. Sturkenboom

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

125 Citations (Scopus)

Abstract

Background: In August 2010 reports of a possible association between exposure to AS03 adjuvanted pandemic A(H1N1)pdm09 vaccine and occurrence of narcolepsy in children and adolescents emerged in Sweden and Finland. In response to this signal, the background rates of narcolepsy in Europe were assessed to rapidly provide information for signal verification. Methods: We used a dynamic retrospective cohort study to assess the narcolepsy diagnosis rates during the period 2000-2010 using large linked automated health care databases in six countries: Denmark, Finland, Italy, the Netherlands, Sweden and the United Kingdom. Results: Overall, 2608 narcolepsy cases were identified in almost 280 million person years (PY) of follow up. The pooled incidence rate was 0.93 (95% CI: 0. 90-0.97) per 100,000 PY. There were peaks between 15 and 30 year of age (women > men) and around 60 years of age. In the age group 5-19 years olds rates were increased after the start of pandemic vaccination compared to the period before the start of campaigns, with rate ratios (RR) of 1.9 (95% CI: 1.1-3.1) in Denmark, 6.4 (95% CI: 4.2-9.7) in Finland and 7.5 (95% CI: 5.2-10.7) in Sweden. Cases verification in the Netherlands had a significant effect on the pattern of incidence over time. Conclusions: The results of this incidence study provided useful information for signal verification on a population level. The safety signal of increased narcolepsy diagnoses following the start of the pandemic vaccination campaign as observed in Sweden and Finland could be observed with this approach. An increase in narcolepsy diagnoses was not observed in other countries, where vaccination coverage was low in the affected age group, or did not follow influenza A(H1N1)pdm09 vaccination. Patient level analyses in these countries are being conducted to verify the signal in more detail.

Original languageEnglish
Pages (from-to)1246-1254
Number of pages9
JournalVaccine
Volume31
Issue number8
DOIs
Publication statusPublished - 6 Feb 2013

Keywords

  • ASO3B adjuvant
  • Background rates
  • Incidence
  • Influenza vaccine
  • Narcolepsy

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