Scientists hoping to explain how a swine flu vaccine caused narcolepsy among Europeans may have to dream on. Stanford University researchers have retracted a major study they authored last year that sought to explain why some people, especially children, were abruptly falling asleep after getting the vaccine, known as Pandemrix.
The retraction doesn’t disprove a link between the Pandemrix swine flu vaccine and narcolepsy, an incurable sleep disorder. But it’s a setback for researchers who have been trying to discover a physiological mechanism for the link. Last December, Emmanuel Mignot, a sleep researcher at the Stanford School of Medicine in California, published a paper with several colleagues in Science Translational Medicine that suggested the link was caused by “molecular mimicry.” Since a protein found in the H1N1 swine flu virus resembles hypocretin, a human brain hormone responsible for maintaining wakefulness, the scientists suggested immune cells primed by the Pandemrix shot were attacking brain neurons that produce hypocretin—resulting in narcolepsy.
On July 30, though, Mignot and his co-authors retracted the study, saying they had been “unable to reproduce the key findings reported in the paper.”
Reproducibility is a vital component of scientific research. When experiments produce the same outcome multiple times—preferably by different labs—scientists consider the results trustworthy. Sometimes, as in this case, a study’s lack of reproducibility sends researchers back to the drawing board.
“We continue to believe that the original scientific hypothesis remains a valid one that needs to be further explored,” said GlaxoSmithKline, the maker of Pandemrix, in a statement following the retraction announcement. “It is crucial that we learn more about how narcolepsy is triggered, and we remain committed to carrying out additional research.”
The association between Pandemrix and narcolepsy has been shown by multiple studies. GSK has discontinued the vaccine, which was never used in the United States. The drugmaker counted about 900 associated cases of narcolepsy, out of 30 million people vaccinated in Europe. Children seem more likely to be affected: About 1 out of every 16,000 children in Finland developed narcolepsy after getting the Pandemrix shot during the 2009-2010 swine flu pandemic.