14 Facts You Should Know About the Flu

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Although it’s late November, it’s not too late to get your flu shot, if you haven’t done so already. The flu season lasts roughly from October to March. It’s recommended you get your influenza vaccination early in the flu season. That means getting it in October, which will help ensure you’re protected when the virus begins circulating. But even if you get your shot now, you’ll still benefit. The vaccine’s protection lasts about six months. The peak of flu season, when the risk is highest, varies from year to year but most often strikes in February. Peak time also varies by location. Bear in mind that it takes two weeks for the vaccine to become fully effective.

In spite of many misconceptions about its effectiveness, the flu shot is an essential protective measure. The following flu facts-both new and old-highlight how and why you should take the necessary steps to avoid an encounter with this unwelcome seasonal visitor.

1. Your risk for developing serious flu complications rises after age 65. Aging weakens the immune system, making it less able to defend the body against the flu virus and other germs. Some flu complications are relatively mild, such as sinus and ear infections, but others can be frightening, including pneumonia and sepsis, a life-threatening immune response to infection throughout the body.

2. It’s a myth that you can get the flu from receiving a flu shot. Injectable vaccines can’t cause the flu because they’re made either with a version of the virus that has been inactivated, or “killed,” or with only components of the virus. It’s unlikely, but you could develop flulike symptoms such as a low-grade fever and aches after receiving the shot, and they usually pass in a day or two. You might also have been exposed to a flu virus before you were vaccinated or within the two weeks following your shot when antibodies are still developing. In rare cases (one or two shots per million), the vaccine can cause a serious immune-system disorder called Guillain-Barr syndrome. If you develop weakness or tingling in the legs after receiving a flu shot, see your doctor.

3. The vaccine reduces but doesn’t eliminate your risk for coming down with the flu. However, if you get vaccinated and still end up developing flu symptoms, they will likely be milder and easier to live with than if you had skipped the shot. And the vaccine will help prevent more serious complications, including life-threatening infections.

4. If you’re over 65, ask your doctor about getting a high-dose flu shot. To help compensate for the natural waning of immunity in older adults, a vaccine containing four times the normal level of antigen (which triggers the body to produce virus-fighting antibodies) is available. The vaccine, Fluzone High-Dose, is approved for people 65 and older. The Centers for Disease Control and Prevention doesn’t take a stance on whether older men and women should opt for the high-dose vaccine, so ask your doctor if it’s right for you.

5. You can safely get a flu shot if you have an egg allergy. Most flu vaccines are made with viruses that were grown in eggs. That exposes vaccine recipients to a tiny bit of egg protein, which doctors once feared could cause adverse reactions in people allergic to eggs. But the American College of Allergy, Asthma and Immunology says the concern is unfounded, based on substantial evidence. While vaccines made without eggs are available, such as the so-called recombinant flu vaccine (Flublok), there’s no reason to seek them out. Moreover, patients with egg allergies no longer need to be observed for 30 minutes after receiving a flu vaccine.

6. Be cautious if you take prescription or over-the-counter medicines for relief of flu symptoms. Many of these products contain the pain reliever acetaminophen (Tylenol). During cold and flu season, there’s a spike in the number of people who unintentionally exceed the recommended daily dose of acetaminophen, which is 4,000 mg (milligrams), according to a study published in the June issue of the British Journal of Clinical Pharmacology. Taking too much acetaminophen is associated with liver damage. If you use flu medication and also take acetaminophen for daily aches and pains, you can easily exceed the safe limit of this pain medicine, so always read labels.

7. If you use the drug methotrexate, consider taking a two-week break from it after getting a flu vaccine. Methotrexate is used to treat rheumatoid arthritis (RA)and some other conditions, but studies show that it can render the flu vaccine less effective. In the June issue of Annals of Rheumatic Diseases, South Korean researchers showed that three-quarters of RA patients who took a two-week holiday from methotrexate after a flu shot responded well to the vaccine compared to just over half of the patients in the group that remained on the drug. The two-week period was deemed short enough to keep flare risk to a minimum. Ask your doctor before altering any drug regimen.

8. Everyone ages 6 months and older should get a flu shot with few exceptions. If you’ve had a prior severe allergic reaction to the flu vaccine, you shouldn’t be vaccinated. If your immune system is compromised, don’t get the nasal spray version of the vaccine. If you have ever had Guillain-Barr syndrome, ask your doctor before getting a flu shot. And if you’re running a fever, wait until it’s gone.

9. You could spread the flu to others just by breathing. Covering up when you sneeze or cough is courteous, but you might pass the flu to others by merely exhaling, says a study published in the January issue of the Proceedings of the National Academy of Science. Researchers used a device to capture the exhaled breath of college students who had developed flu symptoms one to three days earlier. They detected infectious flu virus in 39 percent of the samples collected during normal breathing-in other words, coughing and sneezing weren’t needed to project germs into the air. Experts say that humans can spread the influenza virus by air to people who are six feet away. So, if you have the flu, stay home-you’ll feel better and keep others from getting sick.

10. Once you develop flu symptoms, you’re contagious for up to one week. You can even pass the virus on to others before you begin to ache or sniffle since you’re contagious about a day before you notice any symptoms. The germs can live on surfaces for up to 48 hours-so clean frequently touched items such as doorknobs, tables, and cabinet handles with disinfectant, which may reduce flu transmission. Wash your hands often with soap and water. If soap and water aren’t available, use an alcohol-based hand rub.

11. The flu can set the stage for other conditions, some serious. For most patients, a case of the flu means a week or so of feeling miserable, after which symptoms gradually fade. But influenza can spin off secondary diseases and conditions, particularly in older men and women and the very young. Pneumonia is the most common flu complication, which can be caused by the virus itself or bacteria that attack the lungs. Flu can also trigger severe inflammation in the heart, brain, kidneys, or muscles or throughout the body (sepsis). The flu can also worsen existing conditions such as asthma and cardiovascular disease.

12. A bout of the flu may be associated with an increased heart attack risk. The risk for heart attacks rises in the winter months, and doctors have long suspected that flu infections might be a cause. A Canadian analysis in the January 25 issue of The New England Journal of Medicine offers additional support for that theory; it found that heart attack risk rose sixfold within the first week after patients were diagnosed with the flu. In the analysis, those more likely to have a heart attack were people who were 65 and older, had an influenza B infection, and never had a prior heart attack. However, the association might apply only to patients whose symptoms are severe enough to warrant a doctor’s visit and not to those who have milder symptoms.

13. Not all hospital employees are required to get flu vaccinations. You might think that doctors, nurses, and other hospital employees would be ordered to get flu shots as a way of lowering the likelihood of transmitting the virus to already vulnerable patients. But while the portion of hospitals that require staffers to be vaccinated has risen in recent years, a study in the June issue of JAMA Network Open found that nearly 40 percent of U.S. hospitals lack such a requirement. Veterans Affairs hospitals are particularly lax: Just 4 percent require healthcare workers to protect themselves (and, by association, their patients) by getting a flu shot.

14. Last year’s flu vaccine offered limited protection, which may be true this year, too. This isn’t a new problem, as “mismatches” between the vaccine and the flu virus occur from time to time. Vaccine composition is based on scientists’ predictions of which strains are most likely to be circulating during the next flu season. However, vaccine production takes months, and during that time the dominant strains may change. Moreover, most flu vaccines are made by growing viruses in eggs, a process that can cause the germs to mutate so they no longer match the virus targeted originally. Overall, last year’s flu vaccine was 36 percent effective, meaning it lowered the risk for getting sick by about one-third. It was only 25 percent effective against the H3N2 influenza virus, which caused the most illness. A study in the April issue of Clinical Infectious Diseases predicts that this year’s flu vaccine will only be 20 percent effective against the H3N2 virus-but that’s still better than no protection.