Study offers clue to link between swine flu shot, narcolepsy

WASHINGTON (AP) — One vaccine used in Europe during the 2009 swine flu pandemic was linked to rare cases of a baffling side effect — the sleep disorder narcolepsy.

The vaccine Pandemrix never was used in the United States, and was pulled off the market abroad, but reports of narcolepsy in Finland and several other countries sparked questions globally about flu shot safety.

About a year after mass vaccinations began against a new strain of H1N1 flu, called swine flu at the time, some European countries reported rare cases of narcolepsy in recipients of GlaxoSmithKline's Pandemrix but not in people given other flu vaccines.

[...] some unvaccinated people who caught the flu harbor the antibodies, too, he said, and a study from China found H1N1 infection itself may increase narcolepsy risk.