Several pedestrians wearing masks in front of an advertisement for flu shots.

Though the severity varies from year to year, some kind of flu epidemic is almost a certainty every winter. But this year, with the COVID-19 pandemic still unfolding, public health officials are warning of something unusual: a “twindemic,” with both diseases causing illness at the same time. 

“We’ll have a substantial period of time where we’ll have both flu and COVID circulating,” says Erica Shenoy, MD, PhD, an infectious diseases physician and the associate chief of infection control at Massachusetts General Hospital in Boston.

There’s not an approved vaccine for COVID-19 yet. That’s one key reason health experts are urging, with even more doggedness than usual, that people get their flu shots this season.

The spread of COVID-19 is still uncontrolled in most of the U.S., but with the flu shot, we already have the tools we need to reduce the flu’s toll on Americans and our healthcare system. Here, what to expect from this year’s flu season and what you need to know to stay safe.

Why This Year's Flu Shot Is So Important

Some early signs hint at a potentially light flu season. The Southern hemisphere’s flu season, which is sometimes seen as a clue to what the Northern hemisphere’s may look like, has been mild. That could be in part because of the measures being taken to limit the spread of COVID-19, including social distancing, limiting crowds, and requiring masks, says William Schaffner, MD, a professor of medicine in the division of infectious diseases at the Vanderbilt University School of Medicine in Nashville, Tenn.

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A glance at the U.S. data toward the end of the most recent flu season also supports that hypothesis, says Daniel Solomon, MD, an infectious diseases physician at Brigham and Women’s Hospital and Harvard Medical School in Boston. Around the end of March and the beginning of April—about the same time the strictest stay-at-home and social distancing measures were put into place to control the spread of COVID-19—cases of flu dropped much more quickly than they usually do.

“COVID-19 and flu are spread the same way,” Solomon says, so it makes sense that limiting the spread of one would help stop the spread of the other, too. 

Still, even in the best of times, the Southern hemisphere’s flu season is an imperfect predictor, and that could be even more true this year, Schaffner says. For instance, one reason some countries have reported low flu numbers could be the difficulty of collecting flu data in the midst of the pandemic. Solomon says that in the U.S., many fewer people were seeing the doctor, and many fewer flu tests were being done. That means the drop in cases could simply reflect a lack of testing, rather than a lack of infections. Also, masking and social distancing have been unevenly enforced and followed across the U.S., so their usefulness will vary from place to place.

In any case, colder weather means more time indoors, in closer proximity with other people, giving viruses even more opportunity to spread. And that means your risk of getting sick, whether from the flu or COVID-19, will rise in the winter. 

The flu shot won’t protect you against COVID-19. But it will cut your risk of flu. Last year’s, for example, prevented 39 percent of cases among people who received it. If you get a flu shot and still get the flu, the vaccine will reduce your likelihood of getting severely ill from the disease. Even the vaccine formulated for the 2018 to 2019 season, which scientists judged to be just 29 percent effective, prevented an estimated 4.4 million illnesses, 58,000 hospitalizations, and 3,500 deaths, according to the Centers for Disease Control and Prevention.

Avoiding all that illness helps keep hospitals from becoming overburdened. That’s good for society, but it also benefits you as an individual. “When hospitals are overwhelmed, we have decreased access to care and resources for anyone who needs it,” Solomon says. “If [intensive care units] are at capacity and you have a heart attack, what if we don’t have a bed or ventilator to take care of you?”

Getting Your Shot

Amid the pandemic, you might be wary of going out in public to get a flu shot. But there are options for doing it safely.

Your local pharmacy can have you in and out in just a few minutes, Schaffner says. And many doctors’ offices and clinics are setting up procedures specifically for giving flu shots quickly, such as designated clinic hours just for vaccines, or even drive-up vaccinations. The important thing is to call ahead of time so you know what to expect, Schaffner says. “What you don’t want to do is wait in a clinic somewhere for a half-hour before it’s your turn to be vaccinated.” And both you and the person vaccinating you should be wearing masks.

In past years, the flu vaccines available have been either trivalent, meaning protective against three strains of flu, or quadrivalent, protective against four strains. But this year, the CDC says vaccine manufacturers estimate that 99 percent of all flu vaccines available will be quadrivalent, which means chances are good that you’ll be able to have the extra protection of a quadrivalent vaccine. 

That includes two shots that are especially formulated for and available only to people 65 and older: Fluzone High-Dose, which contains higher levels of antigen (the substance that creates an immune response) than the standard shot, and Fluad, which contains an “adjuvant,” an ingredient designed to boost your immune system’s response to the shot. Studies suggest that both of these options may provide better protection for older adults than the standard vaccine. (If you can’t find one of these vaccines, however, it’s still important to get the regular shot.)

The addition of a fourth strain of vaccine to Fluzone High-Dose and Fluad is good news because older adults are particularly vulnerable to flu. People 65 and older usually account for half or more of all flu-related hospitalizations. Unlike the flu, there’s no vaccine for COVID-19, which also puts older people at greater risk for hospitalization, admittance to the intensive care unit, and death. Getting a flu shot will help keep you healthy.

The CDC recommends getting your vaccine in September or October. The flu shot takes about two weeks to become fully effective, and you want to be protected before the season begins to ramp up. Kids older than 6 months but younger than 8 years old who’ve never had a flu vaccine before (or who’ve only ever had one dose of vaccine in a previous year) need two doses of flu vaccine, spaced at least four weeks apart. If your child falls into that category, get the first dose of vaccine as soon as you can so that you can get the second shot before the season begins.

One final recommendation that the CDC has issued for flu vaccines in light of the COVID-19 pandemic: If you have a confirmed or suspected case of COVID-19, get your doctor’s okay before you get a flu shot. The CDC recommends that people who could still potentially transmit COVID-19 wait until they’re no longer contagious before seeking out a flu vaccine, in order to keep from potentially spreading COVID-19 while getting a shot. 

What to Do If You Get Sick

In a normal year, because most people recover from the flu without treatment, many who develop flulike symptoms wouldn’t need to see a doctor. In fact, a doctor might simply advise you over the phone how to care for yourself, Solomon says, to prevent you from having to come into a clinic and potentially expose others to the flu. 

But that practice will have to change this year, he says, because there is not an easy way to tell the difference between a case of flu and a case of COVID-19 based solely on symptoms. “For patients that have nonspecific symptoms of respiratory viral illness, the only way to distinguish is through a diagnostic test,” he says. 

That means if you start to experience symptoms of a respiratory virus, such as fever, coughing, and more, Erica Shenoy at Massachusetts General recommends calling a doctor sooner rather than later. “Let your doctor know what’s going on and they can make a decision about bringing you in for an evaluation,” she says. (You should also stay home and isolate yourself from others as much as possible, and wear a mask if you do have to leave the house to visit a doctor.) 

Diagnosing a case of COVID-19 as soon as possible is critical, Solomon says, so that you (and in some cases public health authorities) can alert your contacts to the possible exposure. It’s likely that you may also get tested for the flu at the same time. Even if your flu test is positive, it doesn’t rule out the possibility that you could be infected with COVID-19 simultaneously. 

Still, a positive flu test means you may be a good candidate for antiviral drugs such as oseltamivir (Tamiflu). Flu antivirals are recommended for the people who are most at risk for complications, including older adults, young children, and people with underlying health conditions. But those drugs work best when taken within the first 48 hours of the onset of symptoms—another reason to contact a healthcare provider when you first start feeling sick.