Registry study confirms increased risk of narcolepsy after vaccination with Pandemrix in children and adolescents and shows an increased risk in young adults
Tuesday, March 26, 2013
A large Swedish registry study confirms the increased risk of narcolepsy after vaccination with Pandemrix in subjects 20 years and younger. The study also shows an increased risk in young adults (21-30 years). The risk declines gradually with increasing age. No associations with increased risks were concluded for any of the other studied neurological and immune related diseases.
The Medical Products Agency, in cooperation with the Karolinska Institutet and seven counties/regions in Sweden, has undertaken a large registry study in which 3,3 million vaccinated and 2,5 million unvaccinated individuals were compared regarding the risks of being diagnosed with any of more than 50 neurological and immune related/autoimmune diseases under study. The study period ranged from 1 October 2009 to 31 December 2011.
- This is a very extensive and important study which gives valuable knowledge regarding the safety aspects of the pandemic vaccine Pandemrix, says Professor Ingemar Persson, at the MPA.
The study showed a three-fold increased risk for having narcolepsy diagnosed over the study period in subjects 20 years and younger at time of vaccination. The increased risk is slightly lower compared to results from an earlier registry study in Sweden. This discrepancy may be explained by an increase of diagnosed cases of narcolepsy also in unvaccinated children and adolescents. The increased risk during the study period corresponds to an absolute risk increase of approximately four additional cases of narcolepsy per 100 000 person-years.
A two-fold increased risk of narcolepsy after vaccination with Pandemrix was also shown in young adults (21-30 years) while a lower magnitude was observed in the age group 31-40 year. No increased risk was observed for individuals 40 years and older. However, it is not possible to specify an exact age where an increased risk is no longer present.
Furthermore, the study results do not support an association with an increased risk for any of the other studied neurological and immune related/autoimmune diseases.