The Best Time to Get Your Flu Shot—Plus 5 Other Surprising Flu Facts

Flu season is officially here! And even though the Centers for Disease Control and Prevention (CDC) estimates between 9.2 and 35.6 million contract the flu each year, there are a lot of myths and misunderstandings surrounding the influenza virus.

Here, Dr. Sarah Park, MD, FAAP, Hawaii State Epidemiologist and Chief of the Disease Outbreak Control Division for the Hawaii Department of Health shares the facts—and dispels the myths—about the flu, so you can stay healthy this season.

There are only two types of the influenza virus—types A and B—that can cause the seasonal flu. According to Dr. Park, however, many patients believe the flu can be caused by exposure to weather, bacteria and other factors: “I’ve heard people call a stomachache the ‘stomach flu,’ or they have a cold and they’re calling it the flu. Only the flu virus can cause the flu. It’s pretty distinct.”

Because they share symptoms, it can be hard to distinguish between a common cold and the flu; generally, cold symptoms are milder. If you’re pregnant, over age 65 or have a chronic illness or weakened immune system and have symptoms like a fever, chills and muscle or body aches, contact your healthcare provider. It’s important for high-risk groups to seek medical care to avoid potential complications.

Eating a well-balanced diet, exercising and getting plenty of sleep are key to good health—but they won’t necessarily protect you from catching the flu. No type of person is more or less susceptible to the flu virus, but some people are more likely to contract a more severe flu than others. “People with underlying respiratory conditions, like asthma, can have more complications related to the flu or have a prolonged bout of the flu,” says Dr. Park.

People who are healthy, overall, can generally bounce back after contracting the flu. But those with underlying conditions, or people in higher-risk groups, such as pregnant women, the elderly or people living with chronic illnesses, may require hospitalization, antiviral medications or additional treatments.

Although the flu shot can cause side effects like soreness and swelling at the site of injection, headache and nausea, it cannot cause the flu. Vaccines contain inactivated virus—so they’re no longer infectious—or components that look similar to the flu virus, so your immune system is ready when it encounters the real thing.

Dr. Park explains, “[The flu vaccine] should not make you sick because the protein in it cannot make you sick. It’s more likely that you were infected waiting in line at the doctor’s office or pharmacy. It takes two weeks before immunity [from the shot] is fully developed, so if you’re exposed to someone contaminated in that time, you’re going to get sick.”