Factors that may influence influenza vaccine effectiveness

Currently, seasonal flu vaccines are designed to induce high levels of protective antibodies against hemagglutinin (HA), a protein found on the surface of the influenza virus that enables the virus to enter a human cell and initiate infection. New research found that higher levels of antibody against a different flu surface protein -- neuraminidase (NA) -- were the better predictor of protection against flu infection and its unpleasant side effects.