Vaccination against flu can trigger a potentially debilitating neurological disorder called Guillain-Barre syndrome in rare cases according to Canadian researchers, although they do stress that these findings should not make people shy away from getting their shots.
Lead author of the study by the Institute for Clinical Evaluative Sciences (ICES), Dr. David Juurlink, said, "It is very, very small," referring to the risk of Guillain-Barre syndrome (GBS). He said, "It's roughly for every million people vaccinated, we're talking about one or two extra cases of Guillain-Barre syndrome that would not have happened otherwise."
Juurlink explained, "the risk for an individual patient here is marginally greater than being struck by lightning. What we don't want is people running away from the flu vaccine because of this infinitesimal risk of a bad side-effect."
However although the risk is small, Juurlink, an ICES scientist and an internal medicine and clinical pharmacology specialist at Sunnybrook Health Sciences Centre in Toronto, said, "This a material risk, this is not some runny nose or rash that goes away. It's an illness that is potentially fatal and I think it speaks to the importance of . . . the process of informed consent."
"I think the job for doctors and for us as scientists is to try to convey this risk so that people know what they're getting into, that they're aware of the meaningful risks of the vaccine. But at the same time, balance that message with a discussion of the benefits."
Dr. Barbara Yaffe, associate medical officer of health for Toronto, said this research confirms previous studies that linked vaccinations to a tiny boost in risk for GBS. She said it is among the risks and benefits outlined to anyone getting flu shots at Toronto public health clinics, which began providing free vaccinations against this year's likely flu strains on Monday.
She said, "It is important for people to know that this is an extremely rare disease and there is a very slight increased risk . . . However, overall the benefits of this vaccine far outweigh any of the risks. And we know that the vaccine prevents 70 to 90 per cent of infections in healthy people."
The symptoms of flu include fever, aching muscles and respiratory symptoms which is often a consequence of not being vaccinated. And for some such as the elderly and young children influenza can prove to be fatal. Every year, around 500 and 1,500 Canadians die from complications of the flu, most of them elderly and young children.
Yaffe said, "We know that the vaccine can prevent 80 to 90 per cent of deaths in people over 65 years of age in (long-term care) institutions."
In comparison to these figures the risk of developing Guillain-Barre syndrome is very small about 10 per one million people worldwide. The disorder occurs when immune system cells mistakenly attack nerve cells that support the muscles, usually beginning in the legs.