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Why Fit People Get The Flu

Seasonal influenza is more likely to be the result of bad luck than bad health.

Despite the flu shot’s availability, only around 40 percent of adults decide to get vaccinated each year. But I think most everyone—including the fit and healthy—should say yes to the shot. 

The flu is always nasty, but some years it hits harder than others. (Over the past few months, Australia’s been hit with a particularly severe flu strain, and some experts say it could predict a rough flu season for the U.S.) Seasonal influenza can leave even the fittest of athletes in bed for a week or two with the chills or sweats, headache, fatigue, and respiratory congestion. (I had the flu back in med school—it’s not something you want to mess around with.) If you need more convincing, here are five reasons to opt in for the shot.

1. Catching the flu is often just bad luck.

Good health, adequate sleep, a balanced diet, and a strong fitness regimen can certainly help fight off the flu, but sometimes catching it is like drawing a bad hand. Touch the wrong handrail without washing your hands, or sit next to a coughing coworker at the next office lunch, and the virus could be yours, regardless of your health status or sickness track record.

2. It protects everyone else around you.

While a serious bout of the flu can hospitalize anyone, people with a compromised or weak immune system, like older or sick folks, babies, and pregnant women, are especially at risk. Children under six months and people with a life-threatening allergy to the shot have to skip the vaccine.

3. It can’t give you the flu.

Plenty of my patients say they skip the shot because they hear it can give you the flu, but luckily that’s impossible—the virus in the vaccine we give is inactive, or dead. (It doesn’t cause miscarriage, neurological disorders, Alzheimer’s, or heart attacks either—there’s no validation to those conspiracy theories.) That said, the body can have an immune system response after getting the shot, which is why you might feel slightly achy or run a mild fever for a day or two after. Those who become really sick after getting the shot likely were exposed to the flu before the vaccine had a chance to work. (It takes around two weeks from the time you get pricked for the vaccine to kick in, which is why it’s good to get your shot as soon as it’s available. The flu season starts in October, peaks around December, and can last as late as May.) 

4. It’s imperfect—but it’s still your best shot.

The effectiveness of the vaccine varies from year to year. (Last year it reduced the risk of flu by 60 percent.) It’s made new each year by inserting specific strains of the flu virus—the ones experts believe will run rampant this year—into hen eggs, where it grows, and then is killed and purified before it’s injected into your deltoid. The reason it doesn’t prevent 100 percent of flu cases is we may not correctly predict the predominant strains each year, or we may get the strains right but they mutate by the time flu season starts. Even if you catch a flu strain that’s not in the shot, you’ll still receive cross-protection from the vaccine, which can temper your symptoms and the severity of your sickness.

5. Supplements and healthy eats alone can’t prevent the flu.

Some people find that Vitamin C, D, and zinc can help keep the flu at bay or mitigate symptoms, but the shot is the only thing we can unequivocally say helps protect you from the flu, aside from good hand-washing hygiene. It’s a solid bet—unless you like spending your sick days actually in bed.  

Dr. Ahn is a clinical instructor of internal medicine at NYU Langone Health.