Paging Dr. Hamblin: I Don’t See the Upside of a Flu Shot

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Julian Montague

Editor’s Note: Every Wednesday, James Hamblin takes questions from readers about health-related curiosities, concerns, and obsessions. Have one? Email him at

Dear Dr. Hamblin,

I’m perfectly healthy. I’m 42 and I exercise routinely, eat a whole-food, plant-based diet, and have excellent biomarkers. If I get the flu, chances are it will be mild and run its course. So why risk any potential negative side effects of a vaccine? To protect me against something that I might still get even with the shot? Even though I’m sure the risk is low, why should I potentially jeopardize my health? I guess I see only downsides and no upside.

Todd Kelly

Philadelphia, Pa.

Your concerns are widely shared, and your question is important. The answer is especially worth considering because the same logic that guides your decision will apply to the coronavirus vaccines in coming years.

Let’s start with the downsides. Any moral decision starts with accurately assessing the risk of taking an action. In this case, it’s as close to zero as anything modern medicine has to offer. If I were going to focus on risks, I’d be more worried about you getting hit by a car on your way to the pharmacy or doctor’s office than anything that might happen because of the shot.

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Influenza vaccines come in a few types. For healthy American adults like you, the most commonly used variety is the shot. It contains an inactivated form of the virus—either segments of an actual influenza virus’s genetic material or synthetic mimics of those segments. In any case, it can’t cause the flu. Getting the flu from a segment of the virus’s genetic material is impossible. It’s like the difference between inhaling a bee’s wing and inhaling an actual bee.

The only type of flu vaccine that contains a living virus is the nasal spray. But even that can’t cause the flu. The nasal vaccine contains a “live attenuated” virus, meaning it can’t invade human cells and replicate, so it’s like inhaling a bee without its stinger and genitals. Why inhale a whole bee at all, you ask? Well, compared with shots, these live-virus vaccines can more reliably induce a broader immune response. Generating a sufficient immune response is, of course, the goal.

It’s also the source of any symptoms that might arise after the shot. Most people will have some mild soreness or redness at the injection site. A significant minority will have some fatigue or a headache. These symptoms are a result of your immune system reacting to the proteins that have just been injected into your muscle. Unpleasant as they may be, you could think of them as a sign of your immune system getting stronger, like being sore after one of your workouts. Even if you feel a little uncomfortable, none of these symptoms is comparable in scale or severity to having the flu itself. Like COVID-19, influenza is not a disease that completely spares healthy young adults. Some years it largely does, but other years see thousands of hospitalizations and even deaths. In 1918, to take the worst example, influenza killed millions of young, healthy people.

Vaccination carries nothing close to that level of risk. The one scary-sounding, longer-term complication that has been associated with the flu shot, if not definitively linked to it, is something called Guillain-Barré syndrome, an autoimmune condition that results when the immune system misfires and attacks parts of the nervous system, causing muscle weakness. In some cases it leads to temporary paralysis of certain muscles. It can happen in the days and weeks after all sorts of viral or bacterial infections (including COVID-19)—any of a menagerie of things that trigger the immune system to go into attack mode. The Centers for Disease Control and Prevention and global-health agencies suggest that the odds of developing Guillain-Barré syndrome after receiving the flu shot are about one or two in a million. And if that sounds too risky to countenance, consider that you’re much more likely to get Guillain-Barré after an actual case of the flu than after getting a vaccine.

So, really, this is sort of like talking about how seat belts may cause redness or irritation on bare skin and, in rare cases, can cause internal bleeding and organ damage during a serious car accident. If you focus on those risks, wearing a seat belt sounds like a bad idea. Why take a chance? But the value of seat belts becomes obvious when you shift your focus to the danger of going without a device that saves tens of thousands of lives every year.

Likewise, when weighing the risks of getting a flu shot, you have to consider the much more relevant risks of not getting vaccinated. We get used to health risks—such as deaths from car accidents, heart disease, gun violence, and influenza—as they lose their novelty and start to take them for granted, but that doesn’t make them any less dangerous. Somewhere between 10,000 and 60,000 Americans die of the flu each year. Combine that with the effects of so much illness and missed work, and the virus’s annual impact on the U.S. economy is about $90 billion.

This brings us to the upside: If everyone got a flu shot, we could bring those numbers down to about zero. Vaccination is a measure that we undertake to remove ourselves from the pool of susceptible people who can become vectors of disease. You have a great opportunity to do an essentially risk-free thing to play your part in saving thousands of lives. And there’s really no opting out. Whatever you choose, it affects everyone. It’s a personal decision in the same way that driving on the sidewalk is a personal decision.

This is true of getting any vaccine, but especially flu shots, because of the nature of the virus. Influenza mutates so rapidly that each year’s vaccines are based on modeling predictions about which strains will spread most widely. Some years those models work pretty well, and other years they don’t. Even in a good modeling year, a flu shot offers only partial immunity: Some people who get the shot will still be susceptible to the flu. The imperfection means it’s especially important that everyone gets vaccinated to achieve some degree of herd immunity. When you have a more reliably effective vaccine, you can get to herd immunity with a smaller percentage of the population being vaccinated. But with the flu vaccine, we always need to aim for 100 percent participation. Each year, about half of Americans get vaccinated.

A partially effective vaccine has one other important effect: It can make the disease milder even if it doesn’t prevent an infection. That means a lower likelihood of going to the hospital and fewer days of being sick. Even if that doesn’t matter to you personally—maybe you have unlimited sick days, or maybe you like being sick (I don’t know)—a shorter course of disease means you’re less likely to infect other people. That’s ultimately what vaccination is about.

The flu is a global disease that kills more than 500,000 people every year. Someday it will again become a pandemic that kills millions. The rates of death are much higher in countries with less developed health-care systems. The currently available influenza vaccines are difficult to use in low- and middle-income countries without the systems required to vaccinate everyone every year. You and I are lucky to live in a wealthy country and have easy access to a free vaccine. For people like us to forgo it is morally unconscionable.

“Paging Dr. Hamblin” is for informational purposes only, does not constitute medical advice, and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. By submitting a letter, you are agreeing to let The Atlantic use it—in part or in full—and we may edit it for length and/or clarity.