Researchers in Canada have found that for every million doses of the H1N1 pandemic vaccine that were administered in 2009/10 there were two extra cases of Guillain-Barré syndrome which can be fatal in extreme cases.
The benefits of vaccination still outweighed the risks, they concluded as the risk of death from H1N1 in the region was one in 2,500.
It was found the increased risk was between 12 per cent and three fold, due to small numbers involved.
The disease, which can rapidly cause progressive muscle weakness and temporary paralysis, can be triggered by minor infections such as colds and sore throats. It can take a year to recover fully.
The Health Protection Agency in Britain has examined rates of the disease here during and after the pandemic and found there was no increase in vaccinated people.