Narcolepsy and swine flu vaccine

There have been several reports suggesting that the swine flu vaccine may cause narcolepsy in rare cases due to its stimulating effect on antibodies that disable sleep-regulating brain cells.

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Narcolepsy

Narcolepsy is a chronic disorder of the central nervous system that affects the ability of brain cells to regulate sleep cycles as normal.

A large number of neurons in the hypothalamus are usually responsible for producing the orexin hormone, which is also known as hypocretin, that helps make individuals feel awake. These neurons are destroyed or disabled in patients with narcolepsy, thereby causing these individuals to fall asleep more frequently than usual. Management of the condition currently involves a combination of medications to aid sleep at night and stimulants to maintain wakefulness during the day.

Both the pathogenesis of the disorder and the precise cause of the neuronal destruction are highly variable; however, it is generally believed to be an autoimmune response. The antibodies responsible for this may be triggered by certain infections, including influenza.

Swine flu vaccine

Pandemrix, which is the swine flu vaccine that is manufactured by GlaxoSmithKline, is believed to trigger an immune response that may cause the onset of narcolepsy in rare cases.

This reaction likely occurs due to the similarity of the H1N1 proteins and the neurons in the hypothalamus that produce the orexin hormone. This leads to a rare immune response that destroys the brain cells that have an effect on sleep regulation.

In affected patients, symptoms of narcolepsy were reported to present within a few months following vaccination with Pandemrix. However, it is worth noting that, since these initial findings, vaccinated individuals  have received greater attention in this area and may have received an earlier diagnosis of narcolepsy from other causes as a result.

Study: Narcolepsy liked to swine flu vaccines

Epidemiological association

The association between narcolepsy and the swine flu vaccine has been observed in epidemiological data, which noted a rise in the incidence of narcolepsy in countries that utilized Pandemrix to prevent swine flu during the pandemic.

It is estimated that for every 55,000 vaccinations, one case of narcolepsy can be attributable to the vaccine as compared to the general population. However, there are various other possible causes of the condition; therefore, it is not possible to declare with certainty that Pandemrix can take full responsibility for the epidemiological observations.

Mechanism of action and research

Although there were several different swine flu vaccines used during the pandemic, Pandemrix exhibited a stronger association with narcolepsy as compared to those developed by other companies such as the Focetria vaccine by Novartis.

Both the Focetria and Pandemrix vaccines contain a protein that is similar in structure to the orexin receptor; however, Pandemrix has a higher concentration of the protein than Focetra. As a result, it has been hypothesized that this protein induced an autoimmune response that destroyed the orexin cells in the brain and caused narcolepsy.

This effect was tested in individuals that had received the Pandemrix vaccine and supported by the results, which showed that 85% of them had elevated levels of antibodies that target the receptor. Accordingly, none of the individuals in the control group that received the Focetria vaccine exhibited elevated levels of the antibodies.

There have been several studies that have been published on similar observed effects of the swine flu vaccine that has been distributed in various countries worldwide. This remains true for various age groups, from young children to adults, that have received the Pandemrix swine flu vaccination.

References

Further Reading

Last Updated: Mar 17, 2021

Yolanda Smith

Written by

Yolanda Smith

Yolanda graduated with a Bachelor of Pharmacy at the University of South Australia and has experience working in both Australia and Italy. She is passionate about how medicine, diet and lifestyle affect our health and enjoys helping people understand this. In her spare time she loves to explore the world and learn about new cultures and languages.

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