A new study affirms that the 2009 H1N1 flu vaccine, developed to counter the flu pandemic, does not substantially put people at increased risk of Guillain-Barré syndrome. Guillain-Barré syndrome is a disorder in which a person's immune system damages nerves, causing weakness and in some cases paralysis.
The study, conducted at five centers throughout Europe, was published in the latest issue of BMJ.
The concern about Guillain-Barré dates back 35 years. That’s when a vaccine with an added substance called an adjuvant, which stimulates the immune system, appeared to make users of the vaccine seven times more likely to develop the disease. That vaccine, developed by the United States, was withdrawn. Although adjuvanted vaccines developed after 1976 have shown no similarly heightened risk, concern about their safety has remained high.
“Even though the studies repeatedly showed risk estimates well below the sevenfold increase of 1976, they do not provide reassurance that there is no increase in risk after seasonal influenza vaccination,” the authors write.
Guillain-Barré, a rare disorder that affects one to two people out of 100,000, has no known cause. However, about half of all cases occur after a viral or bacterial infection. Weakness and tingling in the legs are early symptoms of the disease. In severe cases, the disorder causes total paralysis and unassisted breathing becomes impossible. Recovery can take from a few weeks to a few years, and a small number of people with the disorder will experience a relapse.