Q: Why do I need to get a flu vaccine every year, while other vaccines last for years, or life?

According to the Centers for Disease Control and Prevention, flu shots are needed every season for two reasons. The body’s immune response from vaccination declines over time, so an annual vaccine is needed for the strongest protection. Additionally, because flu viruses are constantly changing, the formulation of the flu vaccine is reviewed each year to try to match the three or four strains in the flu shot with those expected to be circulating during the upcoming flu season.

Researchers have been working on a universal vaccine that could last for years and provide better protection against all strains of influenza. Researchers at Oxford University have just launched a two-year study of such a vaccine.

Current flu vaccines work by inducing the immune system to produce antibodies targeting the proteins on the surface of the cell. Those proteins change from year to year and from strain to strain. The universal vaccine would target proteins inside the flu virus which do not differ as much. The new vaccine would also work by producing more T-cells to kill the virus, rather than relying on antibodies.

The researchers hope the universal vaccine will provide protection for anywhere from two to four years with a single shot. But it may be years before the clinical trials are completed to determine whether the vaccine is safe, effective and long-lasting.