Original ArticleIncidence of narcolepsy in Norwegian children and adolescents after vaccination against H1N1 influenza A
Introduction
In 2009, a pandemic of influenza A (H1N1 subtype) was expected in Europe. As a result, Norwegian health authorities instituted a campaign for mass vaccination with the adjuvanted vaccine Pandemrix® from October 2009 to January 2010. The vaccination coverage was 45% in the total population of five million inhabitants, and in individuals ages 4–19 years approximately 50% were vaccinated. Most vaccinations were performed during November and December 2009 (Fig. 1).
In August 2010 there were alerting reports of a sudden and marked increase in new cases of narcolepsy in children and adolescents who had been vaccinated with Pandemrix® in Finland and Sweden. Therefore, an investigation of the situation was initiated in Norway.
Section snippets
Methods
Medical institutions and practitioners in the four Norwegian health regions were called upon to report all new cases of excessive daytime sleepiness (EDS) and possible narcolepsy occurring after the vaccination period. New cases were registered by the National Institute of Public Health in cooperation with the Norwegian Resource Center for AD/HD, Tourette Syndrome, and Narcolepsy. The data were collected during the following 120 weeks after the vaccination period. The date of symptom onset was
Results
470,000 children were vaccinated in the period from November 1st, 2009 to January 5th, 2010, comprizing approximately 50% in this age group. Fifty-eight children (23 boys, 35 girls) were reported with confirmed narcolepsy after vaccination. Age distribution was 4–19 years with a mean age 10.5 years (Fig. 2). In addition, two children were still under clinical investigation, and therefore were not included in the reported results.
The median latency from vaccination to onset of symptoms was 11
Discussion
The incidence of narcolepsy in Norway before the vaccination period is unknown. A previous study from 2009 has shown a prevalence of 0.022%, which is comparable to other European countries [2], [3], [4], [5]. The incidence is therefore assumed to be similar to what has been found by other sleep centers in Europe and is estimated to be around 0.5–1 of 100,000 individuals per year [6]. This is in accordance with the recording of five children with confirmed narcolepsy and five children with
Conclusion
Fifty-eight children (mean age, 10.5 years) developed narcolepsy with cataplexy and hypocretin deficiency during the first 2 years following vaccination with Pandemrix®. The incidence in the first year was more than 10 per 100,000 individuals, with a marked cluster during the first 6 months. The incidence was reduced to 1.1 per 100,000 individuals the second year, which is not statistically different from the incidence of 0.5–1.0 per 100,000 individuals per year among the unvaccinated children
Conflict of interest
The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2013.03.020.
References (29)
- et al.
The incidence of narcolepsy in Europe: before, during and after the influenza A(H1N1)pdm09 pandemic and vaccination campaigns
Vaccine
(2013) Narcolepsy in childhood
Sleep Med Rev
(2009)- et al.
A putative link between childhood narcolepsy and obesity
Sleep Med
(2004) - et al.
The Norwegian immunization register-SYSVAK
Eurosurveillance
(2012) - et al.
Prevalence of narcolepsy with cataplexy in Norway
Acta Neurol Scand
(2009) - et al.
Epidemiology of narcolepsy
Sleep
(1994) - et al.
Prevalence of narcolepsy symptomatology and diagnosis in the European general population
Neurology
(2002) - et al.
The epidemiology of narcolepsy in Olmstedt county, Minnesota: a population.based study
Sleep
(2002) - et al.
Clinical and therapeutic aspects of childhood narcolepsy–cataplexy: a retrospective study of 51 children
Sleep
(2010) - et al.
Narcolepsy in prepubertal children
Ann Neurol
(1998)