Ever Wondered How Long the Flu Shot Lasts? We Asked the Experts

You've decided to get the flu shot to steel your body against the tiny invaders known as influenza. So, how long does this stuff last? "The shot lasts long enough to protect against the flu for one flu season," said Dr. Honore Lansen, MD, of One Medical.

In other words, the vaccine you got last year won't protect you from this year's flu. And while this year's shot should shield you until flu season wraps up in the Spring, you'll need another one next Fall. That's because each year's vaccine is different. There are a number of strains of influenza, and "the vaccine tries to predict the strains that will be most prevalent in a given year, but it's not a perfect science," said Dr. Stephanie Long, MD, also of One Medical. "The flu shot is specifically created for the upcoming season, which is why you should get vaccinated each year."

Experts recommend that you get vaccinated before flu cases kick up in October — or as soon as possible, if you miss that window. How long you're protected may depend on your immune system, according to Dr. Jena Sussex-Pizula, MD, at University of Southern California Internal Medicine. "People who have great immune responses may have protection for years, whereas elderly patients or those with complex medical conditions may only have protection for several months," she told POPSUGAR.

Either way, the message is the same: "The flu virus itself mutates so rapidly that a flu shot is needed every year to keep up with the new strains of circulating influenza virus," Dr. Long said. You heard her — go get it!