Study Finds Factors That May Influence Flu Vaccine Effectiveness

The long-held approach to predicting seasonal influenza vaccine effectiveness may need to be revisited, new research suggests. 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 conducted by scientists at NIAID 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. Neuraminidase, which is not currently the main target antigen in traditional flu vaccines, enables newly formed flu viruses to exit the host cell and cause further viral replication in the body.

The findings, from a clinical trial in which healthy volunteers were willingly exposed to naturally occurring 2009 H1N1 influenza type A virus, appeared online Apr. 19 in the open-access journal mBio. 

“Each year, between 3,000 and 49,000 people in the United States die as the result of seasonal influenza and its complications,” said NIAID director Dr. Anthony Fauci. “Annual vaccination against seasonal flu continues to be the most effective way to protect against infection, and this new study provides some interesting clues about how we might improve the level of protection that flu vaccines provide.”