Columbia University Medical Center

Is It Too Late to Get a Flu Shot?

Dr. Seth Feltheimer, an internist at CUMC, answers some common questions about the flu this season.

Why do some people feel sick after getting a flu shot?

The flu shot takes two weeks to activate. A patient may get sick after the shot if he or she has a percolating infection or flu at injection time.

What are my chances of getting the flu if I’ve had a flu shot?

The shot offers 60 percent protection to those exposed to the flu; 40 percent will experience flu symptoms or a weaker version of the flu, depending on their age, health, and immune system.

Are there any risks to getting a flu shot? Should some people not get one?

There are no risks to the shot. The only people who should not get a flu shot are those who are highly allergic to eggs.

What happens if I can’t get a flu shot, or I don’t want to? Are there other preventive measures I can take?

Number 1: Use the flu mist. But note that it’s less potent than the flu shot.

Number 2: Take precautions. Wash your hands frequently. Use hand-sanitizer. Disinfect shared work and home areas.

(More: Proper hand-washing essential during flu season)

How do I know it’s the flu and not something else (such as norovirus or a cold)?

The symptoms will be more prolonged and worse if you have the flu—you’ll have a higher fever, for example.

When does a person infected with the flu become contagious? When does contagiousness end?

People become contagious one day before symptoms start and stay contagious for 5–7 more days.

 Is it too late to get the shot? And if I’m already sick with something, should I still get a shot?

It’s not too late! If you’re already sick, you should wait until your fever subsides to get the shot.

Is this year’s flu vaccine protective against the most common strains we’re seeing?

Yes—it’s protective against three strains of flu: influenza B, H1N1, and H3N2.

If you DO have the flu, what’s the best thing you can do to care for yourself?

Stay home and treat the symptoms. If you have a fever, take acetaminophen or ibuprofen. Drink lots of fluids.

At what point should you seek medical attention for the flu?

If your symptoms persist or worsen (for example, a high fever or a cough with complications) or if you do not improve in a few days, call your doctor.

An earlier version of this article was published on January 16, 2013.

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