As flu season approaches, you probably don't need a reminder to be immunized against influenza, since you can't step into a pharmacy or supermarket without seeing signs imploring you to roll up your sleeve. The shot is an essential protective measure in spite of many misconceptions about its effectiveness. 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.
That ideally means getting a flu shot in October, which will help ensure you’re protected when the virus begins circulating. But if you put off getting vaccinated, you’ll still benefit from a shot later in the season, which lasts roughly from October to March. 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.
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.
Injectable vaccines can’t cause the flu because they’re made with an inactivated ("killed") version of the virus or with only components of the virus. It’s unlikely, but you could develop flu-like symptoms such as a mild fever after getting the shot. They usually pass in a day or two. You might also have been exposed to a flu virus before you were vaccinated or shortly after, when antibodies are still developing. Rarely, the vaccine can cause a serious disorder called Guillain-Barré syndrome. If you develop weakness or tingling in the legs after a flu shot, see your doctor.
However, if you do develop 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.
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 CDC 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.
Most flu vaccines are made with viruses grown in eggs. That exposes recipients to a tiny bit of egg protein, which doctors once feared could cause adverse reactions in people allergic to eggs. But experts now say the concern is unfounded, based on substantial evidence. While egg-free vaccines are available, such as the "recombinant flu vaccine" (Flublok), there’s no reason to seek them out. Patients with egg allergies also no longer need to be observed for 30 minutes after a flu shot.
Many contain the pain drug 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 milligrams, a study in the British Journal of Clinical Pharmacology found. Taking too much acetaminophen can cause liver damage. If you take acetaminophen as well as flu medication containing it several times a day, you can easily exceed the safe limit, so always read labels.
This drug, used to treat rheumatoid arthritis (RA) and some other conditions, may render the flu vaccine less effective. In a South Korean study, 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 stayed on the drug. Ask your doctor before altering any drug regimen.
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-Barré syndrome, ask your doctor before getting a flu shot. And if you’re running a fever, wait until it’s gone.
So found a study in the Proceedings of the National Academy of Sciences. 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. So, if you have the flu, stay home—you’ll feel better and keep others from getting sick.
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 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. Wash your hands often with soap and water. If they aren’t available, use an alcohol-based hand rub.
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 adults and young children. Pneumonia is the most common flu complication. Flu can also trigger severe inflammation in the heart, brain, kidneys, or muscles or throughout the body (sepsis), and it can worsen existing conditions such as asthma and cardiovascular disease.
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 New England Journal of Medicine offers additional support for that theory; it found that heart attack risk rose six-fold within the first week after patients were diagnosed with the flu. 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.
While the proportion of hospitals that require doctors, nurses, and other hospital staff to get an annual flu shot has risen in recent years, a study in JAMA Network Open found that nearly 40 percent of U.S. hospitals still lack such a requirement. VA hospitals are particularly lax: Just 4 percent require health care workers to protect themselves (and, by association, their patients) by getting a flu shot.
Vaccine composition is based on predictions of which influenza strains are likely to circulate during the next flu season. But vaccine production takes months, during which time the dominant strains may change. And the vaccine-growing process itself can cause the germs to mutate so they no longer match the original virus. Last year’s shot was 36 percent effective overall—and only 25 percent effective against the H3N2 virus, which caused the most illness. Still, any protection is better than none.
Current flu-shot antibodies attach themselves to portions of the virus capable of mutating, or changing, which is why the vaccine must be reformulated each year. To remedy this, research teams are attempting to create universal vaccines that attach to regions on the influenza virus that aren’t known to mutate. Clinical trials of some experimental universal flu vaccines are underway.