Why the flu shot can't give you the flu

Experts say it's impossible to get the flu from the flu shot. But here are some reasons people think the shot makes them sick.

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/ Source: TODAY
By Linda Carroll

Just as the current influenza season is getting started, a new study finds a troubling decline in the number of babies and children getting their yearly flu vaccinations.

Researchers in the journal Pediatrics suggest several reasons fewer parents get flu shots for their children, including the rising popularity of the anti-vaccine movement, a lack of confidence in the effectiveness of the flu shots and worries about harmful side effects.

It may be too soon to predict how severe the flu outbreak will be this year; however, there were 142 pediatric deaths during the 2018-2019 flu season. There have been two child deaths so far this year, as of Nov. 2.

A national survey by Orlando Health from 2015 found that many parents are skeptical about flu shots, and more than half of parents surveyed believed that you can get the flu from the vaccine.

In reality, the flu shot can’t and won’t give you the flu, experts stress.

It’s biologically impossible for you to catch the flu from being vaccinated, said Dr. William Schaffner, an infectious disease specialist and a professor of preventive medicine at Vanderbilt University in Nashville.

That’s because the vaccine is constructed from a killed virus. Not only that, but also there are only a couple of proteins from that dead virus in the vaccine. So, nobody’s getting injected with a complete virus.

Those proteins, taken from the surface of the killed virus, are enough rev up our immune system and give it a clear target. But they certainly aren’t enough for the flu virus to reconstitute itself in our bodies.

It might be a cold

For the most part, people are mistakenly assuming that symptoms which coincidentally developed around the time they got the shot were caused by the vaccine. But, Schaffner explained, just because two events occur around the same time doesn’t mean they’re connected.

“We all know the rooster crows before dawn,” he explains. “But we don’t think the rooster makes the sun come up.”

Most of us get our flu shots in the fall, noted Dr. Michael Ison, a professor in the division of infectious diseases at Northwestern University’s Feinberg School of Medicine in Chicago. “That is when rhinoviruses are circulating,” he added. “Most people think a cold is just a stuffy nose,” Ison said. “But you can get really sick from a cold. In fact, many viruses can make you as sick as the flu does.”

There’s also the issue of where you get your shot, said Dr. Richard Zimmerman, a professor of family medicine at the University of Pittsburgh. “If you go to the pharmacy or to the doctor’s office there’s a good chance someone sitting next to you will be coughing,” Zimmerman says.

Which is not to say you won’t get any symptoms after a flu shot.

Arm pain

About 20 percent of people experience soreness in the arm that got the shot, Zimmerman said. “That lasts about a day and then goes away,” he adds.

Fatigue, headaches

“There are a few people who feel a little fatigued after getting the shot,” Schaffner says. “And a few get a headache. These are all part of the body’s immune response to the vaccine. It’s not influenza.”

You already have the virus

If you were exposed to the flu shortly after being vaccinated your body didn’t have enough time to marshal its forces against the virus. The shot doesn’t reach full effectiveness until two to three weeks after vaccination, Ison said.

So, there's no good reason not to get the shot. Even people with egg allergies are now cleared to get it.

“Don’t linger. Run to your health care provider and get vaccinated right away," he said.