Don't want to get narcolepsy? Then have a flu vaccine!
Emmanuel Mignot, who will be speaking at the September Conference of Narcolepsy UK has put the cat among the pigeons with his latest paper published in Annals of Neurology on August 22nd a journal of the American Neurological Association.
For the new study, the researchers looked at the data of 906 patients who were diagnosed with narcolepsy in Beijing between September 1998 and February 2011, and determined the patients' month of onset of cataplexy and sleepiness. They conducted brief phone interviews with 154 patients whose narcolepsy appeared after October 2009, the date of the first H1N1 vaccination administered in China for the 2009-10 flu pandemic. The researchers also queried the patients about their history of seasonal flu, H1N1 vaccinations and other diseases.
The results for the European narcolepsy community are startling.
Following the pandemic, rates of narcolepsy tripled, compared with other years. But fewer than 6% of the interviewed patients had received a flu vaccination, suggesting that their narcolepsy was unrelated to the vaccines used in China.
Last year, European research found that the H1N1 vaccine Pandemrix was associated with a ninefold increase in narcolepsy cases in children in Finland. The European Medical Agency suggested a link between Pandemrix, some other event and developing narcolepsy. But that vaccine contains adjuvants – additives that boost the body's immune response to it; the additives are not included in vaccines used in the U.S. and China.
Tests and research continue to determine what this “other event” might be. Perhaps Dr Mignot suggests it might be the H1N1 virus itself. As we know several interesting research projects have suggested links between upper airway infections (including strep throat) and the development of narcolepsy.
There is a history of influenza-type diseases causing neurological conditions. At its height H1N1 was thought to have the same sort of disease potential as the great Spanish Flu pandemic of 1918. One of the most interesting side effects of that latter pandemic was the number of individuals that succumbed to what medical authorities at the time called “seasonal somnolence” or “encephalitis lethargica”. Has the same thing happened again?
Alas, we don’t know for sure. While we may have a strong correlation we don’t have cause and effect yet. What we do know from the Mignot paper is that he also found a strong seasonal narcolepsy component; with November being the least likely month to be diagnosed with narcolepsy and April most common. January to May saw a statistically higher narcolepsy pattern than the rest of the year; there was a five- to seven-month delay between the seasonal peak in flu/cold or H1N1 infections and the peak in narcolepsy onset occurrences. Was that pattern caused by getting a winter upper airway infection? We don’t know, but a lot of interesting research will be carried out in the coming months and years to find that out.
At the moment all we can say is that it is highly possible that an influenza like disease could trigger an immune response in susceptible individuals; and that response could cause narcolepsy. Dr Mignot himself said the work is exciting because it provides insight on how the disease is triggered. "We're much closer to understanding what's happening in the autoimmune destruction of hypocretin cells."
Many UK families whose children developed narcolepsy will be most interested by this comment from Dr Mignot."It's very possible that being vaccinated with a mild vaccine, one without the adjuvants in question, blocks you from getting a big infection that could increase your risk of narcolepsy." His work in China does suggest that getting vaccinated and avoiding influenza may provide a protective benefit to patients.
As for the differences between the findings of the study and what has been observed in Europe, Dr Mignot said it's possible that the strong immune response prompted by the (adjuvant-containing) Pandemrix vaccine increases the risk of narcolepsy. He emphasized, however, that more study is needed and that people shouldn't avoid getting vaccinated.
"Even with Pandemrix, it's still a very small risk - and there's a bigger risk from dying of an infection if you don't get vaccinated," he said.