The Link Between an H1N1 Vaccine and Narcolepsy

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Vaccines have been associated with any number of bizarre side effects — but putting people to sleep? That’s a new one.

Last week, a preliminary Finnish study found that the H1N1 flu vaccine may have contributed to a spike in narcolepsy cases in that country among 4-to-19-year-olds. In 20o9-10, health officials said, 60 children and adolescents in that age group had developed narcolepsy, and 52 of them had received the flu vaccine Pandemrix.

Based on the early data, Finnish officials said, people who received the injection had a nine-fold increased risk of narcolepsy over those in the same age group who had not been vaccinated.

Use of the vaccine was halted in Finland in August 2010, after concerns about it first arose; it’s not clear how many youngsters and teens were vaccinated with Pandemrix, but about half of Finland’s 5.3 million population received the shot during the winter of 2009-10, according to the AP.

On Tuesday, a World Health Organization panel said that genetic factors may have played a role in Finland’s Pandemrix-narcolepsy cases. WHO tested 22 narcolepsy patients and found that all had a gene commonly associated with narcolepsy. About 30% of people in Finland have that particular gene, compared with 15% in the rest of Europe, according to Patrick Zuber, WHO’s top vaccine safety official.

To date, 12 of the 47 countries that used the vaccine, including Sweden and Iceland, have reported upticks in narcolepsy cases after vaccination. The AP reports:

WHO’s Global Advisory Committee on Vaccine Safety said in a statement Tuesday that it agreed with Finnish authorities that there was a “strong association” between the vaccination, the genetic makeup of the patients, and the narcolepsy cases.

But since a coincidental correlation cannot be ruled out, and as narcolepsy after swine flu vaccination has been reported in only a few countries so far, the panel recommended that Pandemrix continue to be administered to children.

Narcolepsy is a rare and chronic neurological disorder that causes extreme fatigue and unexpected episodes of sleep. But the cases reported in Finland lasted only a few months following vaccination and were not permanent. According to WHO, this is the first time the condition has been associated with a vaccine:

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.

Pandemrix is not available in the United States because it contains an adjuvant — a compound that boosts immune system response, reducing the needed dose of the vaccine. The FDA has not approved flu vaccines that contain adjuvants for use in the U.S.