Influenza increases the narcolepsy risk

Sleeping sickness risk increases due to flu illnesses

24/08/2011

Researchers have shown a link between influenza infections and the so-called sleeping sickness (narcolepsy). A flu illness increases the risk of subsequent narcolepsy, report study leader Emmanuel Mignot and colleagues from Stanford University in California in the current issue of the journal „Annals of Neurology“.

As part of their study, the scientists had examined about 900 Chinese narcolepsy patients and revealed it to be clear evidence, „that winter infections with influenza A and / or streptococci are the trigger of narcolepsy.“ About five to seven months after a flu epidemic, according to the researchers, the number of narcolepsy diseases has also increased. Following the particularly severe influenza epidemic in the winter of 2009/2010, narcolepsy cases have even tripled, according to the latest study. A connection between the occurrence of sleeping sickness and the flu vaccines could exclude the researchers, however, at least for the vaccine used in China.

Sleeping sickness due to flu shot?
Most recently, the European Medicines Agency (EMA) recommended a waiver of the use of the influenza vaccine Pandemrix® in adolescents (vaccine causes narcolepsy) based on recent epidemiological studies from Finland and Sweden, safety data from health authorities and case reports from various EU countries. Because this could possibly increase the risk of narcolepsy, according to EMA. This assessment was also supported by the preliminary results of an epidemiological study by the ECEC's Vaccine Adverse Events Surveillance and Communication (VAESCO) Network. The scientists around Emmanuel Mignot of Stanford University in California, however, exclude an association with the flu vaccine in the approximately 900 Chinese narcolepsy patients. According to the researchers, only 5.6 percent of narcolepsy patients were previously vaccinated against influenza. In fact, however, the flu itself poses an increased risk of narcolepsy, the experts explained. As Study Director Emmanuel Mignot emphasized, is „the discovery that there is no association with the vaccine“ particularly important. Because this could be seen as an indication that „could even increase the risk of contracting narcolepsy in order to reduce vaccination.“

The connection between the occurrence of sleeping sickness and influenza vaccines was closely examined for the first time following the use of the controversial vaccine Pandemrix in the wake of the swine flu epidemic in 2009/2010. For example, epidemiological studies from Finland came to the conclusion that around nine times more children were diagnosed with narcolepsy after vaccination with Pandemrix than the national average. Subsequent investigations by the World Health Organization (WHO) and the European Medicines Agency revealed that the vaccine appears to be causing the onset of sleeping sickness through interaction with other substances. Which substances cause these interactions, however, remains unclear, although early suspicion of two contained potentiators, so-called adjuvants fell. Whether influenza vaccines without contained adjuvants may also increase the risk of narcolepsy, the scientists around Emmanuel Mignot have now in their recent study using the influenza vaccine used in China reviewed.

The study revealed that there was no increased risk of developing vaccinated narcolepsy patients compared with unvaccinated subjects, the researchers at Stanford University report. Because influenza vaccination reduces the risk of flu and the flu itself should be evaluated as a risk factor for narcolepsy, people should not refrain from a flu vaccine for fear of narcolepsy, said study leader Emmanuel Mignot. Mignot believes that vaccination with a mild flu vaccine without an enhancer could even reduce the risk of narcolepsy. The scientist has been researching sleeping sickness for years, and in 2009, together with his colleagues, proved for the first time that the disease is to be understood as an autoimmune disease. According to the expert, the immune cells of the body apparently erroneously attack nerve cells in which a particular protein is produced. Significant effects such as extreme drowsiness during the day, sleep disorders and sudden muscle failure follow for those affected.

According to the US scientist, around three million people around the world suffer from narcolepsy, with a genetic predisposition to the disease and specific environmental factors that trigger it. According to the researchers, such an environmental factor can be, for example, a wintry cold that is followed by an excessive reaction of the immune system. Since the swine flu vaccine Pandemrix was also found to increase the risk of narcolepsy, certain ingredients also appear to act as disease-causing environmental factors. In order to determine the totality of environmental factors and to explain how the autoimmune disease narcolepsy is provoked by these environmental factors, the scientists say that further investigations will be necessary in the coming years. (Fp)

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Image: Sarah Blatt