Adjuvanted vaccines used during the 2009 swine flu pandemic did not increase the risk of Guillain-Barré syndrome substantially, if at all, according to a Europe-wide study.
Researchers compared flu vaccine exposure in 104 people who developed the syndrome with 25 control subjects matched to each of them.
They found no association between vaccination and Guillain-Barré syndrome, but note they cannot statistically rule out the possibility of a small increased risk remaining. They estimate this risk to be less than three excess cases of Guillain-Barré syndrome for every million individuals protected by the vaccination.
There have been concerns that vaccines could trigger Guillain-Barré ever since 1976, when a vaccine used during a US flu pandemic was linked with the syndrome.