The 2009 human “swine flu” vaccine given to millions of Canadians was associated with twice the normal risk of developing Guillain-Barre syndrome — a rare but potentially paralyzing nerve disorder, Quebec researchers are reporting.
With Guillain-Barre syndrome, or GBS, the immune system attacks the body’s peripheral nerves, causing rapidly progressing muscle weakness and sometimes paralysis.
In a new study led by Quebec City’s Laval University, researchers looked at all suspected and confirmed cases of GBS as reported by doctors — mostly neurologists — and hospital discharge records starting in the fall of 2009, when more than half of Quebec’s population was vaccinated against H1N1 as part of mass immunization campaigns that rolled out nationwide. Quebec’s chief medical officer of health ordered the investigation.
By the end of the year, 4.4 million Quebec residents had received the pandemic vaccine.
Over a six-month followup period between October 2009 and March 2010, 83 confirmed GBS cases were identified; 42 occurred in people who had been recently immunized.
Twenty-five developed symptoms within eight weeks of vaccination; of those, most — 19 — developed the syndrome within four weeks.
Overall, the Laval group calculates that the number of cases that can be attributed to the human swine flu shot was approximately two per one million doses.
The risk of contracting GBS from a normal seasonal flu shot has been estimated at about half that — an additional one case per million people vaccinated.