Narcolepsy and the Pandemrix swine flu vaccine

You will no doubt have heard or seen news that a swine flu vaccine called Pandemrix has been suspected of causing narcolepsy. It is important to understand the full implications of what has happened and how that might affect you. 

Pandemrix was supplied to 30 million people in the European Union as a vaccine against the H1N1 version of swine flu. On the 24th of August Finland suspended its national vaccination programme after doctors reported 8 cases of suspected narcolepsy after patients had been given Pandemrix. Over the last three days Sweden has reported 10 cases, six in France and one in Germany and Norway. There have been no reported cases in Britain to date.

To put this in context that is LESS than .0001% of the people who had the vaccine.

Out of the 30 million that were given the vaccine, statistically at least 100,000 of them will have narcolepsy. As the syndrome is so under-diagnosed, 80% of the total will not have a diagnosis of narcolepsy. It could be that doctors who were looking for a reaction to the vaccine discovered patients with an existing condition. We don’t know and with the small number of cases confirmed so far it will be very difficult to prove one way or the other.

After research carried out by Swiss and French scientists we can now say that for the majority of those with narcolepsy, it has been brought on by an auto immune response. An antibody was discovered that attacked and killed a specific area of the brain that produced a neuropeptide called hypocretin. Hypocretin is needed to regulate sleep. Scientists have not yet discovered the trigger for this autoimmune response. It could be a reaction to a seasonal virus, it could be genetic; it could be a host of things including, though unlikely, a reaction to a vaccine. 

If there has been an auto immune reaction, doctors could test a small sample of spinal fluid for hypocretin. If no hypocretin is present it would indicate that the production areas had been attacked, indicating an auto immune reaction. However if this was a recent response or had happened some time ago could not be proven, unless the patient had been checked prior to vaccination and found to have normal levels of hypocretin. 

The European Medicines Agency will now investigate if there is any link, including how many people would normally be expected to suffer narcolepsy so this 'background rate' can be compared to with the number of cases observed after vaccination. Considering the small numbers of cases reported so far, it is difficult to see how they could judge these were caused by the Pandemrix vaccine.

Unless the EMA changes its advice or a significant number of new cases are discovered, the recommendation remains to take the vaccines that are offered to you. As long as narcolepsy remains such an under-reported condition, the possibility of cases like this appearing are high. 

Published date: 

Thursday, 1st December 2011