Each spring, public health experts make predictions about what the most common flu virus variants will be for the upcoming fall flu season. Vaccines are then produced to protect against those variants. When this prediction is accurate, the flu vaccine is more effective. But the flu virus can change over time, so some predictions are less accurate. Some believe that happened this year. Still, even a mismatched vaccine will lower a person’s chances of severe flu.

Variants included in the 2024/2025 flu vaccine are influenza A(H1N1) virus, an influenza A(H3N2) virus, and an influenza B/Victoria virus.

We won’t know the true effectiveness of the flu vaccine this year until after the flu season is over, but based on data from the Southern Hemisphere it is likely around 35% effective, which is lower than last year’s 42% but still close to the typical range of 40% to 60% effectiveness.

There are several factors that determine how many people get sick with the flu each year including which strain of the vaccine is dominant and how many people get vaccinated.

For the first year since the COVID pandemic began, the number of deaths from seasonal influenza is higher than the number of deaths from COVID.

Even if you still get sick after getting the flu vaccine, being vaccinated reduces your risk of being hospitalized or getting severe illness.

Even if you already got sick with the flu this season without being vaccinated, you could still get sick with a different strain than the one you already had. It is not too late to get the flu vaccine to reduce your risk of serious illness.

We will not know the effectiveness of this year’s flu vaccine in the U.S. until the flu season is over and public health officials are able to examine the data.