A swine flu vaccine may have triggered sleep disorder problems in children, researchers warn today.
Narcolepsy is a chronic sleep disorder involving daytime sleepiness, affecting 25 to 50 per 100,000 people. Its onset has previously been linked with having the flu.
Professor Elizabeth Miller of the Health Protection Agency in London, UK, and her team looked at the risk of narcolepsy in 245 children in England aged four to 18 years given the A/H1N1 2009 vaccine (called Pandemrix) since October 2009.
They used information from sleep centres to identify which children went on to develop narcolepsy. A total of 75 developed narcolepsy, 56 of whom also had cataplexy as a symptom – a brief loss of muscle tone triggered by strong emotion.
The rate of narcolepsy was over 14 times higher for children who had the vaccine than for similar children who had not.
Details appear in the British Medical Journal today (27 February). The authors say that the increased risk they saw after the vaccine "indicates a causal association, consistent with findings from Finland". But they point out that the risk "might be overestimated by more rapid referral of vaccinated children".
In the study from Finland, Pandemrix was linked to a 13-fold increased risk of narcolepsy in children and young people aged four to 19 years. As in this study, it usually occurred within three months after vaccination.
Pandemrix is unlikely to be used again, adds the team, but they believe their results have implications for other similar vaccines.
Miller, E. et al. Risk of narcolepsy in children and young people receiving AS03 adjuvanted pandemic A/H1N1 2009 influenza vaccine: retrospective analysis. BMJ 27 February 2013 doi: 10.1136/bmj.f794 [abstract]
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