Some surveys indicate that almost 30% of people think receiving the flu shot can actually lead to getting the flu. This belief, according to the CDC, likely stems from common vaccine side effects like headaches, fever, and muscle aches, as well as injection site reactions such as pain and redness.
Dr. Samantha Picking, who oversees immunizations at Walgreens, mentioned that it’s a widespread misconception that the flu vaccine can cause the illness itself. In fact, she explained, most influenza vaccines contain inactivated viruses or parts of them, meaning they can’t cause the flu.
There is, however, a nasal spray version known as a live attenuated influenza vaccine (LAIV), which includes a weakened form of the virus.
Dr. Mark Siegel, a senior medical analyst, reiterated that the vaccines are created from “dead, inactivated, or killed virus,” emphasizing that the flu cannot be contracted from them.
While not everyone experiences side effects from the flu shot, mild symptoms are possible. Picking noted that when people do feel unwell after vaccination, it’s usually a sign that their immune system is responding and building protection.
Side effects can differ from one person to another, but common reactions—like pain at the injection site or low-grade fever—indicate the vaccine is taking effect. Generally, side effects appear soon after the shot and can last a day or two, often manageable with over-the-counter medications.
It’s worth noting that some groups, like women, young children, pregnant individuals, and those receiving higher doses of the vaccine, might be more prone to side effects.
Picking mentioned that while it is technically possible to contract the flu shortly after vaccination, this happens because full immunity takes about two weeks to develop. Hence, if someone gets sick right after their shot, it’s not caused by the vaccine itself—it’s just that they weren’t fully protected yet. This underscores the importance of getting vaccinated early.
The side effects of the vaccine can mimic actual flu symptoms, but the timing and intensity are what set them apart. For instance, flu shot side effects tend to be mild and arise within hours, generally clearing up quickly, whereas real flu symptoms are usually more severe and prolonged.
If you’re feeling a bit under the weather, it’s generally okay to receive the flu shot if you only have mild symptoms—like a basic cold without a fever. However, if you’re experiencing moderate to severe illness, especially with fever, it’s advisable to wait until you’ve recovered before getting vaccinated. Doing so can help ensure an optimal immune response and make it easier to distinguish between vaccine side effects and actual illness.
