No, Flu Shot Side Effects Don’t Mean That the Vaccine Gave You the Flu
People offer up plenty of...questionable...excuses for not getting their annual flu vaccine. Exhibit A: wanting to avoid flu shot side effects that “prove” they’ve caught influenza from the very thing meant to protect them. If only we could grab a bullhorn and shout this from every rooftop: “You can’t get the flu from the flu vaccine,” infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security, tells SELF. Seriously, this is not a thing that is even remotely possible.
Instead, you might experience totally normal side effects from the flu vaccine that may make you think it’s given you the flu when it really hasn’t. Once you read the information below and understand why it’s impossible to contract the flu from the flu vaccine, tell your friends, will you? The more people who know this, the better.
You can’t get the flu from the flu vaccine because it only exposes you to dead, partial, or weakened forms of the influenza virus.
Researchers pick the strains of the influenza virus that go into the vaccine based on data that suggests which will be the most common and dangerous in the upcoming flu season, according to the Centers for Disease Control and Prevention (CDC). This changes each year, which is why doctors recommend that you get your flu vaccine annually.
Although the flu shot is often in the spotlight, the CDC is also recommending an additional form of the flu vaccine for this flu season: the nasal spray.
The shot contains inactivated (completely dead) or incomplete strains of the influenza virus, while the nasal spray contains live attenuated (weakened) strains. The main point is that neither form of the vaccine contains live flu viruses that can thrive in your body, the CDC explains. “You get the flu from being infected with the flu virus,” Richard Watkins, M.D., an infectious disease physician in Akron, Ohio, and an associate professor of internal medicine at Northeast Ohio Medical University, tells SELF. “The vaccine cannot cause the flu.”
However, these dead, partial, and weakened viruses are enough to provoke your immune system to develop antibodies to guard you against live and threatening flu viruses, the CDC explains. It usually takes about two weeks for those to kick in and offer you protection.
The flu vaccine is most likely to cause minor side effects like soreness or a runny nose, but some people can develop flu-like symptoms, too.
Most people won’t experience post-vaccine symptoms at all, according to the CDC. The most common side effect in people who do have symptoms from the shot is soreness at the injection site, Dr. Adalja says.
Other possible flu shot side effects include hoarseness, a cough, fever, aches, headaches, itching, fatigue, and sore, red, or itchy eyes, the CDC says. If you’re going to experience these issues, it’s most likely that you’ll have them soon after receiving your shot and that they’ll only stick around for one to two days.
With the nasal spray vaccine, you could get a runny nose, sore throat, cough, chills, fatigue and weakness, and a headache, the CDC says. These also typically go away within a few days.
Flu vaccine side effects are all signs that your immune system is responding to the dead or weakened influenza strains.
“When you get any type of vaccine, the whole purpose is to expose your immune system to the virus,” Dr. Adalja explains. “Your immune system will start to rev up in response.” Sometimes your immune system does this without causing noticeable symptoms, but other times, you’ll experience a few minor side effects as a result.
“Some of the symptoms might overlap, but it’s not the flu,” Dr. Adalja says. For reference, the flu tends to cause the sudden onset of a fever over 100.4 degrees, achy muscles, chills and sweats, a headache, a dry and persistent cough, fatigue, weakness, nasal congestion, and a sore throat, according to the Mayo Clinic. In young and healthy adults, these symptoms typically abate after a week or two. That’s longer than it takes flu shot or nasal spray side effects to disappear, and these symptoms will be way more intense if you have the actual flu.
If you think you have the flu after getting vaccinated, you might—but it didn’t come from the vaccine itself.
It’s completely possible to pick up the flu in the two weeks between when you get the vaccine and when your antibodies kick in, Dr. Watkins says. The longer you wait to get vaccinated, the higher likelihood you’ll encounter the virus without protection. “This is why people should get the flu vaccine early, in October or November,” Dr. Watkins adds, though better late than never. And even if you do get the flu, you should still go get vaccinated to guard against other strains of the virus, because getting the flu twice in one season is indeed possible.
Beyond that, you can get vaccinated against the flu then pick up something like rhinovirus, which causes the common cold, and which can prompt some similar symptoms to the flu, the CDC says.
Finally, we’d be remiss not to acknowledge that even if you do get the flu vaccine, it’s not 100 percent effective. Does it increase your chances of making it through flu season unscathed? Yes. Does it lower your chances of complications if you do wind up with the flu? Yes. Does it reduce your chances of passing the flu along to vulnerable people like babies and the elderly? No surprise here: yes.
The bottom line is that you should absolutely still get vaccinated even though the vaccine isn’t perfect. Dealing with possible side effects from the flu shot or nasal spray is much, much better than coming down with the actual flu itself.
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