Flu shot lowers risk of rare side-effect in most seasons for most people

TORONTO — A new study suggests that for most people in most flu seasons, getting a flu shot actually lowers their risk of developing a rare neurological condition that has been linked to the vaccine.

The study, by researchers in Ottawa, assesses the net effect of getting a flu shot or getting infected with flu on one's risk of developing Guillain-Barre syndrome.

Guillain-Barre syndrome triggers progressive paralysis that can be fatal but from which most people recover.

All the cases of Guillain-Barre syndrome are not known, but it is recognized that some infections raise the risk of developing the condition and getting a flu shot can increases one's risk slightly.

The researchers, from The Ottawa Hospital, wanted to see if that small increased risk was balanced out or exceeded by the risk posed by contracting influenza.

And they found in most seasons, the risk of developing the condition after catching the flu was higher than the risk of developing it after getting a flu shot.

"The take-home message is that most of the time, in most of the scenarios we're seeing, the vaccination actually reduces your risk," says lead author Steven Hawken, a scientist at The Ottawa Hospital who built the mathematical model on which the research is based.

The study is published in the February issue of the journal Emerging Infectious Diseases.