DEAR MAYO CLINIC: I am 28 and consider myself fairly healthy. I have never gotten a flu shot and have never had the flu. I did receive a COVID-19 vaccine series. Do I really need a flu vaccination? My employer is recommending an influenza immunization for everyone, but I am hesitant. I have heard some people get sick from flu shots.

ANSWER: The Centers for Disease Control and Prevention now recommends that everyone 6 months and older be vaccinated every year against influenza, or flu. Being young and healthy does not protect you against getting the flu. Even someone like you, who has not had influenza in the past, should still get an annual flu shot. In some cases, people may develop minor flu-like symptoms after receiving the vaccine; however, it is important to know the flu vaccine cannot give you the flu.

Influenza is a viral respiratory infection that tends to come on suddenly. The influenza virus is a systemic virus. That means it circulates throughout the body in the bloodstream. Symptoms typically include fever, aching muscles, chills, sweats, headache, feeling tired and weak, coughing, and nasal congestion.

Influenza can cause complications, such as sinus and ear infections, bronchitis, and pneumonia. These complications, particularly pneumonia, can be especially dangerous in young children; pregnant women; older adults; and people who have chronic medical conditions, such as asthma, epilepsy, kidney disease or liver disease, among others. Getting an annual flu vaccine is the most effective way to prevent influenza and its complications.

It is important to note, however, that even though young children and older adults are most vulnerable to complications from the flu, the most severe forms of flu that we have seen have not affected those groups the most. Instead, the most infectious and serious strains of influenza — such as the strain that caused the 1918 worldwide pandemic — have more often affected young, healthy adults. Most cases of death associated with severe flu strains have been in younger adults who were otherwise healthy.

To best protect yourself from the flu, you need to get a flu shot every year. That’s because the vaccines change each year to keep up with rapidly adapting influenza viruses. Because flu viruses evolve quickly, last year’s vaccine may not protect you from this year’s viruses.

After you get a flu vaccination, your immune system produces antibodies that will protect you from the flu viruses. As with any immunization, it can take about two weeks to build immunity after getting vaccinated. After a while, antibody levels for vaccines will start to decline — another good reason to get a booster every year.

Generally, it is a good idea to get a flu shot in the fall, usually in late September or early October. But if you miss that timing, it’s never too late to get a flu shot, as it will still protect you when you are vaccinated. Although the peak flu season is typically during the winter, as we have seen in years past — and especially with COVID-19 — viruses can circulate at any time.

After getting a flu shot, a few people may develop flu-like symptoms, usually a low-grade fever that lasts about a day. In many cases, this happens because those people were previously exposed to a virus that was similar to the vaccine strain, and their immune system is already prepared to respond to it. The fever is a sign of their immune system response, not a symptom of influenza infection.

It is particularly important for women who are pregnant to get a flu shot in order to protect their unborn child. I would suggest that if you have questions or concerns about the flu vaccine, talk with your primary health care clinician. — Dr. Tina Ardon and Dr. Stephen McMullan, Family Medicine, Mayo Clinic, Jacksonville, Florida

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