Study offers clue to link between rare narcolepsy cases, vaccine
WASHINGTON - One vaccine used in Europe during the 2009 swine flu pandemic was linked to rare cases of a baffling side effect - narcolepsy. New research offers a clue to what happened. The vaccine Pandemrix never was used in the U.S., and was pulled off the market abroad, but the sleep disorder reports raised vaccine safety questions. On Wednesday, researchers reported that the H1N1 flu strain contains a protein that is structurally similar to a narcolepsy-related brain cell receptor. They found that flu-fighting antibodies generated by Pandemrix also could latch onto that receptor. Pandemrix contained more of that flu protein than other vaccines. The theory is that high antibody levels could trigger the disease in someone who already was genetically susceptible.