Increased Risk of Narcolepsy in Children Who Received Vaccination for Swine Flu

A study from England shows there is an increased risk of children developing narcolepsy if they received the H1N1 swine flu vaccine.

A study finds an increased risk of narcolepsy in children and adolescents who received the A/H1N1 2009 influenza vaccine (Pandemrix) during the pandemic in England.

The results are consistent with previous studies from Finland and Sweden and indicate that the association is not confined to Scandinavian populations. However, the authors stress that the risk may still be overestimated, and they call for longer term monitoring of the cohort of children and adolescents exposed to Pandemrix to evaluate the exact level of risk.

In 2009, pandemic influenza A (H1N1) virus spread rapidly, resulting in millions of cases and over 18,000 deaths in over 200 countries. In England the vaccine Pandemrix was introduced in October 2009. By March 2010, around one in four (24%) of healthy children aged under 5 and just over a third (37%) aged 2-15 in a risk group had been vaccinated.

In August 2010 concerns were raised in Finland and Sweden about a possible association between narcolepsy and Pandemrix. And in 2012 a study from Finland reported a 13-fold increased risk in children and young people aged 4-19.

But a lack of reported cases in other countries led to speculation that any possible association might be restricted to these Scandinavian populations.

Narcolepsy is a chronic disorder of excessive daytime sleepiness, often accompanied by sudden muscle weakness triggered by strong emotion (known as cataplexy). To evaluate the risk after vaccination in England, a team of researchers reviewed case notes for 245 children and young people aged 4-18 from sleep centres and child neurology centres across England.

Of these, 75 had narcolepsy (56 with cataplexy) with onset after 1 January 2008. Eleven had been vaccinated before onset of symptoms; seven within six months.

After adjusting for clinical conditions, vaccination at any time was associated with a 14-fold increased risk of narcolepsy, whereas vaccination within six months before onset was associated with a 16-fold increased risk.

In absolute numbers, this means that one in 52,000 to 57,500 doses are associated with narcolepsy, say the authors.

They write: "The increased risk of narcolepsy after vaccination with ASO3 adjuvanted pandemic A/H1N1 2009 vaccine indicates a causal association, consistent with findings from Finland. Because of variable delay in diagnosis, however, the risk might be overestimated by more rapid referral of vaccinated children."

While further use of this vaccine for prevention of seasonal flu seems unlikely, they say their findings "have implications for the future licensure and use of AS03 adjuvanted pandemic vaccines containing different subtypes such H5 or H9."

And they conclude: "Further studies to assess the risk, if any, associated with the other A/H1N1 2009 vaccines used in the pandemic, including those with and without adjuvants, are also needed to inform the use of such vaccines in the event of a future pandemic."

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Study: No Link Between Flu Vaccine and Epileptic Seizures

This article discusses how no link was found between the H1N1 Influenza vaccine and the development of epilepsy or seizures.

Epileptics are often encouraged to receive flu vaccines because the risk of seizure increases when a patient has the flu. With more focus recently on vaccine safety and side effects, many are wondering if this preventative measure could actually make conditions worse.

A recent study looked at the risk of epileptic seizures after receiving the vaccine for the H1N1 flu. The study found no evidence of patients having more seizures after vaccination.

Lisen Arnheim-Dahlstrom, PhD, and colleagues from the Karolinska Institute in Stockholm, Sweden examined 373,398 people who received a version of the H1N1 vaccine, Pandemrix, in three counties in Sweden.

Pandemrix was developed by GlaxoSmithKline and began being distributed for the H1N1 flu in October 2009. It was one of four authorized vaccines used during the 2009 flu pandemic known as the swine flu.

The safety of Pandemrix drew attention when cases of narcolepsy occurred in children and teenagers after receiving the vaccine. In addition, the European Medicines Agency (EMA) received reports of epileptic seizures occurring after vaccination.

These reports made further investigation of the drug necessary.

The researchers were able to access records for the 373,398 through the Swedish vaccination register, a database of all vaccinations in Sweden. The patient’s unique personal identification number was then used to look up histories of epilepsy andantiepileptic drugs in other registries.

Within the study population, 7,787 people were considered epileptic during the year before the study and 356,611 were not.

Dr. Arnheim-Dahlstrom and team determined how many of the total study population experienced at least one epileptic seizure during the time period of 90 days before vaccination to 90 days after vaccination. During this 180 day period surrounding the vaccination, 859 people experienced epileptic seizures.

For those previously diagnosed with epilepsy, there was no increase in risk of seizures during the first week after vaccination. During this week, there was an insignificant decrease in risk of seizure for people without epilepsy.

From day 8 to day 30 after the vaccination, there was no increase in risk of seizure for those diagnosed with epilepsy. There was an insignificant increased risk of seizures in people without epilepsy during this time period.

These results dismiss safety concerns with Pandemrix for those with epilepsy.

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The Curious Link Between H1N1 Flu and Narcolepsy

A swell in new cases of narcolepsy in China followed seasonal patterns of flu, including H1N1, according to a recent study led by Dr. Emmanuel Mignot of the Stanford University School of Medicine. The new cases appear to be associated with flu infection itself, not with flu vaccinations.

A peak in cases of narcolepsy — an autoimmune disease that causes people to fall asleep suddenly — occurred about five to seven months after a peak in cold and flu cases in the country, the study found. Onset in the spring was seven times more common than in the winter.

Researchers believe that people have a genetic predisposition to narcolepsy, which may be triggered by some environmental factor, such as an upper airway infection. Reported the New York Times:

Narcolepsy and a related but even rarer illness, cataplexy — a tendency to collapse when swept by strong emotions — are caused by the death of brain cells that secrete hypocretin, which regulates sleep. Those cells, Dr. Mignot explained, are probably killed by autoimmune reactions that stem from winter infections like flu and strep throat.

For several years after the 1918 Spanish flu pandemic, medical authorities described a seasonal somnolence they called "encephalitis lethargica."

Read more: http://healthland.time.com/2011/08/23/the-curious-link-between-h1n1-flu-and-narcolepsy/#ixzz1WTq0Gh2M