Your Questions About the Flu Vaccine

From the WebMD Archives

People come up with all kinds of excuses to avoid getting the flu vaccine.

"I've had the flu and it's no big deal."

"The vaccine will give me the flu."

"There are toxic levels of mercury in the vaccine."

If you listen to these misconceptions and don't get your flu vaccine, you could catch the latest circulating influenza strain and spend a week or more sidelined from work and feeling miserable. Even worse, you could get really sick and wind up in the hospital.

Here are a few reasons why you absolutely need toget a flu vaccine this year:

  • Influenza (the flu) circulates all over the world, and it can affect anyone, regardless of their age or health.
  • The flu can lead to complications like pneumonia, ear infections, and sinus infections. It can also worsen existing conditions, like asthma or diabetes.
  • Each year, thousands of people in the U.S. die from the flu and its complications.

Want to know the truth about the flu vaccine? Read through these common questions and answers to learn how it works, whether it's risky, and why you definitely need to get it.

Do I Really Need a Flu Vaccine?

If you're over 6 months old, the CDC says yes, you need to get a flu vaccination at the start of every flu season. Despite the fact that we tend to label any illness that makes us sneeze, shiver, or vomit as "the flu," true influenza isn't a trivial illness. It can do far worse than just keep you home from work or school for a few days.

"Hundreds of thousands of people each year are hospitalized with influenza. Between 3,000 and 40,000 people die during any influenza season, depending on the strain that's circulating," says Jeffrey Duchin, MD. He's chief of the Communicable Disease Epidemiology & Immunization Section at Seattle & King County Public Health, and an associate professor in medicine in the University of Washington Division of Infectious Diseases.

Although young infants, the elderly, pregnant women, and people with chronic conditions like asthma or heart disease are most susceptible to flu complications (including pneumonia), people of all ages die from the disease each year.

"It's a serious health problem for adults and children. And it's preventable," says Duchin, who is also a member of the CDC's Advisory Committee on Immunization Practices (ACIP). "We have a way for people to avoid unnecessary doctor's visits, to avoid unnecessary antibiotics, and to avoid hospitalization."

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Why Do I Need to Get Vaccinated Every Year?

You might balk at having to visit your doctor or pharmacy every year for yet another dose of the influenza vaccine, but there's a good reason for the repeat visits. The flu bug is a pretty wily creature.

"The virus is sort of tricky in the way it reproduces from year to year, in that it shifts its chemical coating from season to season," explains Geoffrey A. Weinberg, MD, a pediatric infectious disease specialist and professor of pediatrics at the University of Rochester. "Even if you've been good about getting flu shots for several years you need to keep it up, because next year's flu could be very different."

The flu is far less predictable than measles and chickenpox, which only take a couple of childhood immunizations to provide full protection. "Those diseases are caused by only one strain of virus, and they don't shift," says Weinberg.

That annual flu vaccine ritual might soon be coming to an end, however. Researchers have been on the hunt for a universal flu vaccine for several years, and they may be getting close. Recently, they've discovered a more consistent target on the flu virus -- one that could help them finally develop a flu vaccine that provides long-lasting protection.

How Well Will the Flu Vaccine Protect Me Against the Flu?

Each spring, public health experts around the world predict which flu strains are most likely to circulate and cause illness in the coming flu season. Based on their predictions, the flu vaccine is formulated to protect against those three or four strains. When the experts have made a good match, the vaccine is up to 90% effective in healthy adults. For those age 65 and older, a high-dose version of the flu vaccine called Fluzone is recommended when available. It may be more effective at protecting the elderly because their immune systems are more fragile.

Sometimes the flu virus will outsmart the experts and transform itself between their prediction and the beginning of the flu season. It might even change in the middle of a flu season. Then the flu strains in the vaccine won't match the strains in circulation.

Even if the vaccine isn't a perfect match it's still worth getting, experts say. Each vaccine protects against three to four different flu strains, so chances are at least one of them is circulating in any given season. Plus, when you get vaccinated against one strain of flu virus, your body makes antibodies that protect you against related strains, even if they're not exactly the same.

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When Do I Need to Get the Vaccine?

Get vaccinated as soon as the vaccine is available at your doctor's office, public health clinic, supermarket, or wherever else it's offered in your area. "Many people unfortunately wait until cases of influenza are already in their community. That's not a particularly good idea because influenza is very contagious and it travels very quickly," Duchin says. The vaccine takes about two weeks to take full effect, so if your neighbor comes over coughing and sneezing and your immune system isn't yet fully primed against the flu, watch out.

Because experts are never sure exactly when in the flu season the first viruses will hit, earlier is better. Get the vaccine in August or September, and it should protect you through the whole flu season, even if it lingers until March.

Should I Get the Flu Shot or the Flu Spray?

The flu vaccine is available in two forms: the injected vaccine and the nasal spray. The shot is approved for everyone over 6 months.

It's long been advised that people with allergies to eggs should not get the flu shot. However, the American College of Allergy, Asthma and Immunology says the vaccine contains such a low amount of egg protein that it's unlikely to cause an allergic reaction in those with an egg allergy. If you have a severe egg allergy (anaphylaxis), talk to your doctor before getting the flu vaccine. Also, flu vaccines not made with the use of eggs are available.

Talk to your doctor if you have a history of Guillain-Barre syndrome. People who are moderately or severely ill should wait until they recover to get the vaccine.

Intradermal flu vaccines go into the top layer of skin instead of the muscle, which means the needle can be 90% smaller than the kind used for a standard flu injection. Like the egg-free vaccines, this one seems like it would be ideal for babies and kids, but it's approved only for adults 18 to 64.

If you're not a fan of shots, the nasal spray vaccine is a good alternative, but it's only approved for non-pregnant people ages 2 to 49 who are generally in good health without chronic health conditions such as asthma, heart or lung disease, or diabetes. Because the spray contains a live but weakened form of the virus, it's not recommended for people with diseases that interfere with the immune system, such as HIV. It also should not be used in children less than 5 years old with asthma or a history of wheezing in the past year, people with muscle or nerve disorders that can lead to breathing or swallowing problems, and children on long-term aspirin treatment. If you have a stuffy nose or other nasal problem that makes breathing difficult, you should get the shot. However, the CDC now recommends the nasal spray vaccine for healthy children 2 through 8 years old when it is available.

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Can I Catch the Flu From the Flu Vaccine?

You probably know at least one person who claims he or she came down with the flu days after getting a flu vaccine. Though your friend might have felt sick, the vaccine wasn't to blame for the ailment. "It's a very commonly held myth, but it's just that," Weinberg says. "It's absolutely impossible scientifically and medically to get the flu from the inactivated vaccine shot."

You can't catch the flu from the vaccine, because the version of the virus used in flu shots is dead. In the nasal spray vaccine the virus is severely weakened, so it's not likely to cause more than a few sniffles or sneezes. Chances are, your friend either had a bad cold or another respiratory infection, not the flu.

Most side effects from the influenza vaccination are mild, like soreness at the site of the shot, a low-grade fever, or a little achiness. You're actually far safer getting the vaccine then skipping it. "There's a much higher rate of getting complications if you take your chances with the real disease than if you get immunized," Weinberg says.

Can I Get the Flu Vaccine if I'm Pregnant?

You should get the flu shot if you're pregnant. "It's recommended for two reasons," says Duchin. "One is because pregnant women have a higher rate of severe influenza and hospitalizations than non-pregnant women. And if you give the vaccine to pregnant women, you protect their unborn baby for the first 6 months." Pregnant women should only receive the flu shot.

Does the Flu Vaccine Contain Thimerosal?

You might have heard the buzz about thimerosal, a mercury-containing preservative used in certain vaccines. All vaccines that are marketed for use in young children no longer contain thimerosal, but it is still found in some vaccines used in adults, including certain flu vaccines.

Researchers have studied thimerosal extensively, and they haven't found any connection between the preservative and autism or any other serious health risks. Still, if you're worried, you can ask your doctor to use a thimerosal-free vaccine.

WebMD Feature Reviewed by Louise Chang, MD on March 11, 2011

Sources

SOURCES:

World Health Organization: "Influenza."

CDC: "Estimating Seasonal Influenza-Associated Deaths in the United States: CDC Study Confirms Variability of Flu."

Geoffrey A. Weinberg, MD, pediatric infectious disease specialist, professor of pediatrics, University of Rochester.

Jeffrey Duchin, MD, chief of communicable disease epidemiology & immunization section, Seattle & King County Public Health; associate professor of medicine, University of Washington Division of Infectious Diseases.

CDC: "2010-2011 Flu Season."

CDC: "The Nasal-Spray Flu Vaccine (Live Attenuated Influenza Vaccine [LAV])."

CDC: "Seasonal Influenza (Flu) -- Key Facts About Seasonal Flu Vaccine."

FDA: "Thimerosal in Vaccines."

WebMD Feature: "Flu Breakthrough: The Search for a Universal Vaccine."

GlaxoSmithKline.

News release, American College of Allergy, Asthma and Immunology.

CDC: "Nasal Spray Flu Vaccine in Children 2 through 8 Years Old." 

 

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