What are the risks from the H1N1 flu vaccine?

The H1N1 flu vaccine contains trace amounts of dead virus, so you cannot get infected by the vaccine. The side effects are generally similar to those associated with the seasonal flu vaccine.

Most common reactions after getting the H1N1 flu vaccine were minor and included pain, swelling and redness at the injection site. Other commonly reported reactions were fatigue, muscle and joint pain, and headache. In younger children, a fever, drowsiness, irritability and loss of appetite were also reported in low levels. Serious and life-threatening reactions are very rare.

A more serious illness called Guillain-Barré syndrome (a severe paralytic illness also called GBS) has occurred very rarely after the administration of seasonal flu vaccine. All age groups can be affected but GBS is most common in the elderly population. A variety of infectious agents are also known to be associated with GBS including influenza virus and food-borne pathogens. The risk of suffering GBS as a complication from influenza virus is greater than the risk of getting it as a reaction to the flu shot.