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This fact brief was originally published as an experiment to test the concepts behind fact briefs.
Readers should be aware that while there is still a lot of useful information in fact briefs like this one, not all of them reflect Gigafact's current methods and standards for fact briefs. If you come across any that you feel are out of date, don't hesitate to contact us at support@gigafact.org.
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FACT BRIEF

Did an H1N1 vaccine used in Europe cause narcolepsy?

By Esther Honig
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YES

According to the Centers for Disease Control and Prevention, a vaccine used in several European countries during the 2009–2010 H1N1 influenza pandemic was associated with an increased risk of narcolepsy.

The vaccine, manufactured by GlaxoSmithKline plc, was never licensed for use in the U.S. and has not been used since the 2009–2010 flu season.

Later studies of the vaccine, Pandemrix, and a similar GlaxoSmithKline vaccine, Arepanrix, discovered that a protein found in both the H1N1 virus and some H1N1 vaccines blocked the receptor for another small protein, hypocretin, which is associated with wakefulness. Only patients with a particular genetic makeup were affected, suggesting that the vaccine triggered an autoimmune reaction.

Follow-up research from the CDC found no association between narcolepsy and the U.S.-licensed H1N1 vaccine.

This fact brief is responsive to conversations such as this one.
Sources
CDC: Narcolepsy following 2009 pandemrix influenza vaccination in Europe
National Library of Medicine: Canadian Medical Association Journal—H1N1 vaccine and narcolepsy
Science: Antibodies to influenza nucleoprotein cross-react with human hypocretin receptor 2
National Library of Medicine: EBioMedicine—Pandemrix-induced narcolepsy associated with genes related to immunity and neuronal survival
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Gigafact
Between 2020 and 2022, under close editorial supervision, Gigafact contracted a group of freelance writers and editors to test the concepts for fact briefs and provide inputs to our software development process. We call this effort Gigafact Foundry. Over the course of these two years, Gigafact Foundry writers published over 1500 fact briefs in response to claims they found online. Their important work forms the basis of Gigafact formats and editorial guidelines, and is available to the public on Gigafact.org. Readers should be aware that while there is still a lot of relevant information to be found, not all fact briefs produced by Gigafact Foundry reflect Gigafact's current methods and standards for fact briefs. If you come across any that you feel are out of date and need to be looked at with fresh eyes, don't hesitate to contact us at support@gigafact.org.
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About fact briefs published on Gigafact
Fact briefs are short, credibly sourced summaries that offer “yes/no” answers in response to claims found online. They rely on publicly available, often primary source data and documents. Fact briefs are created by contributors to Gigafact —a nonprofit project looking to expand participation in fact-checking and protect the democratic process. See all fact briefs here.