A recently completed Swedish registry study indicates that children and adolescents under the age of 20 have a four times higher risk of developing the sleep disorder narcolepsy if they have received the influenza vaccine Pandemrix® compared to those who are not vaccinated. The results from this study are in line with the results of a similar Finnish study. In the Swedish study 1:33,000 vaccinees developed narcolepsy – in the Finnish study, it was 1:12,000. Most cases were seen in the period immediately after vaccination. Neither the Swedish nor the Finnish study showed an increased risk for adults.
In Denmark, the Danish National Board of Health recommended to only vaccinate children who were more vulnerable to severe or serious influenza, unlike in Sweden where the vaccine was offered to all children and adolescents regardless of their health. In Denmark, 20,800 children and adolescents younger than 18 were vaccinated.
Pandemrix® is not used in Denmark anymore - no reports of narcolepsy
We have had no reports of narcolepsy in Denmark, and there has been no increase in reports of narcolepsy outside the Nordic region. Pandemrix® was used as vaccination against A(H1N1) – the pandemic flu – in 2009/2010. Pandemrix® has not been used in Denmark since the pandemic in 2009/2010.
At a meeting today, the Danish Medicines Agency, the Danish National Board of Health and the Danish State Serum Institute have discussed the new research results from Sweden and Finland. The Danish authorities find that there is no immediate cause for concern in Denmark, but will follow the ongoing investigations of the potential link between Pandemrix® and narcolepsy.
The increased risk for children and adolescents is thoroughly investigated
The Swedish Medical Products Agency continues to investigate why children and adolescents are at an increased risk and why only this particular group is at an increased risk. For this reason, the Swedish Medical Products Agency presently recommends not to give the Pandemrix® vaccine to children and adolescents younger than 20 years of age.
In Finland, it is being investigated whether environmental or genetic influences could have been a contributory factor in the development of narcolepsy after vaccination with Pandemrix®.
At EU-level, work is ongoing to examine the potential link between Pandemrix® and narcolepsy. In autumn 2010, a collaboration of ECDC (European Centre for Disease Control) and other research institutes launched project VAESCO, which addresses epidemiological studies of Pandemrix® in nine countries, including Denmark. The results of these studies will be available during summer 2011, following which the European Medicines Agency (EMA) expects to be able to finalise its assessment.
The results from the Swedish study will furthermore be discussed in the European Pharmacovigilance Working Party in April 2011. The new Swedish results will be included in these discussions together with the results from the Finnish study and results collected worldwide.
Facts about narcolepsy after vaccination with Pandemrix®
In total, at least 30.8 million people in Europe have received the Pandemrix® vaccine. As at 15 February 2011, 339 cases of narcolepsy possibly associated with Pandemrix® have been reported in the EU and EEA.
Narcolepsy is a rare sleep disorder involving sudden sleep attacks. The incidence is approx. ten in a million each year. The cause of illness is not yet established, but it is suspected to be caused by genetic and environmental factors, including infections.