The Nocturnal Brain: Nightmares, Neuroscience, and the Secret World of Sleep

by Guy Leschziner

It was within a year of the vaccination campaign, however, that researchers noticed something rather unusual. Several cases of narcolepsy appeared to be related to one of the H1N1 vaccines used in Europe, called Pandemrix. The numbers of cases of narcolepsy rose dramatically in countries where this vaccine was used, particularly in children, but a similar increase in numbers was not seen in the USA, which used a different vaccine. In later years, the numbers of new cases dropped down to levels prior to this vaccination programme. It was not only the vaccination that was associated with onset of narcolepsy, though. In China, cases of narcolepsy were found to be related to the H1N1 influenza virus itself. Interestingly, in mice bred without intact immune systems, the H1N1 virus has been shown to migrate to the hypothalamus and brainstem, causing sleep disruption directly. Expression of high levels of viral components in these areas of the brain may make them particularly vulnerable to autoimmune damage, if the immune system is intact. So, it is not just the Pandemrix vaccine that appears to trigger narcolepsy, but the flu virus strain itself.