In 2010, following the H1N1 pandemic and the vaccination campaign to reduce its impact, researchers noted a significant increase in a rare neurological disorder, narcolepsy, in Sweden and Finland. Since then researchers have been studying a possible association between a specific H1N1 flu vaccine, Pandemrix by Glaxo-Smith-Kline (GSK) and a sudden onset of the sleep disorder narcolepsy. In those two countries the association seems strong, but the full story is still complicated with many unknowns.
Narcolepsy is a neurological disorder marked by excessive sleepiness, cataplexy (sudden loss of muscle tone, usually triggered by emotions) and disordered sleep. Almost all cases are associated with low levels of hypocretin in the hypothalamus – this is a hormone involved in sleep regulation. Further there is a strong HLA (human leukocyte antigen) association – specifically DQB1*0602. HLA is a group of proteins involved in regulating immune activity. An HLA association strongly suggests that narcolepsy may be an auto-immune disease.
The current synthesis of this information is that narcolepsy occurs in genetically susceptible individuals after some environmental trigger, such as in infection, that causes the immune system to attack and destroy hypocretin cells in the brain.
Last year it was reported that there was a possible increase in narcolepsy, a sleep disorder characterized by excessive sleepiness, in children who had received the Pandemrix brand of H1N1 flu vaccine in Sweden, Finland, and Iceland. However a review of the data did not find a convincing connection, although concluded there was insufficient data at present and recommended further surveillance. A narcolepsy task force was formed in Finland, and now we have their preliminary report.
They conclude that the evidence suggests there is a connection:
Based on the preliminary analyses, the risk of falling ill with narcolepsy among those vaccinated in the 4-19 years age group was 9-fold in comparison to those unvaccinated in the same age group. This increase was most pronounced among those 5–15 years of age. No cases were observed among those under 4 years of age. Also, no increase in cases of narcolepsy or signs of vaccination impacting risk of falling ill with narcolepsy was observed among those above 19 years of age.
The World Health Organization (WHO) has reviewed these results and concluded:
WHO’s Global Advisory Committee on Vaccine Safety (GACVS) reviewed this data by telephone conference on 4 February 2011. GACVS agrees that further investigation is warranted concerning narcolepsy and vaccination against influenza (H1N1) 2009 with Pandemrix and other pandemic H1N1 vaccines. An increased risk of narcolepsy has not been observed in association with the use of any vaccines whether against influenza or other diseases in the past. Even at this stage, it does not appear that narcolepsy following vaccination against pandemic influenza is a general worldwide phenomenon and this complicates interpretation of the findings in Finland.