With all the talk about COVID-19 vaccines and boosters, it's easy to forget that another dangerous respiratory virus is poised to strike — the flu.

Experts worry that we could be heading into a big flu season, especially if enough Americans do not get their annual flu shot, which is now widely available.

"We are worried the incredibly low influenza rates that we saw last season could create a rebound influenza epidemic this year," says Dr. Mark Roberts, director of the Public Health Dynamics Laboratory at the University of Pittsburgh.

Most years as many as 12,000 to 52,000 people die from the flu in the U.S. But the unusually mild flu season last year means that fewer people have immunity to strains likely to be circulating this winter. That could lead to anywhere from 100,000 to 400,000 additional hospitalizations for influenza, according to two recent computer modeling studies done by Roberts and his colleagues.

"It could be really bad — and it could be really bad at a time when there's still quite a bit of COVID-19 filling up our hospitals," he says.

Getting the flu shot remains the single most powerful action a person can take to fend off the days- or weeks-long, wracking muscle aches, fever and sometimes deadly respiratory infection that is influenza.

"Two reasons make getting vaccinated against the flu the wise choice," says Dr. William Schaffner, medical director of the National Foundation of Infectious Diseases. "First, it's been proven year after year that you're in better shape to fight off the flu if you get the vaccine. Second, by getting vaccinated against the flu, you help protect the people around you."

Here's a guide to getting yourself vaccinated against the potentially fatal virus.

I heard that the flu essentially disappeared last year. Do I really need a flu shot this year?

Yes. Last year saw a record-low number of flu cases, likely thanks to widespread mask wearing, remote work and school, and physical distancing. But this year, experts fear that the reopening of schools, decreased adherence to pandemic precautions and surging delta variant infections could create a double whammy: a very serious flu and COVID-19 season. Already, cases of RSV, yet another serious respiratory virus in children, are spiking. "This suggests that flu will be back [too]," says L.J Tan, executive director of the Immunization Action Coalition.

Who should get a flu shot?

Anyone 6 months and older, unless your doctor has specifically recommended that you not get a flu shot because of a prior, rare, severe reaction, says Dr. Lisa Grohskopf, a medical officer in the influenza division at the Centers for Disease Control and Prevention.

When's the best time to get the flu shot?

Why not now?

Flu season starts in October in the U.S. While there's some concern that immunity might wane before the end of flu season in May if you get the vaccine too early, there's not enough data to know the optimal time to get the shot, Grohskopf says.

The CDC says aim to get your flu vaccine by the end of October. By then, cases will have started to mount, and many people will be just a few weeks away from travel for Thanksgiving and Christmas. That said, "getting vaccinated at any time during the flu season [can] still be beneficial," says Dr. Andrew Pavia, chief of pediatric infectious diseases at the University of Utah Health.

Will the flu vaccine definitely keep me from getting the flu?

No. No vaccine is 100% effective. But if you do get the flu, the vaccine is likely to reduce your chance of getting very sick, being hospitalized or dying, Pavia says. Before last year, tens of thousands of people were hospitalized or died from the flu each year, usually people who weren't vaccinated.

Can I get the flu and COVID-19 vaccines at the same time?

Absolutely. The CDC had previously recommended spacing out the timing of the COVID-19 vaccine and other immunizations because the vaccines were so new, but "that guidance has changed," says Grohskopf. The CDC now says it's safe to get both vaccines at once, she says. "The body's immune response and side effects are generally the same as when getting one vaccine alone." If you do get two shots on the same day, expect to get each vaccine in a different arm, which may reduce any pain and swelling that might occur.

What about my COVID-19 booster shot — can I get that at the same time as my flu shot?

Right now, third doses of COVID-19 vaccine are authorized for many people. If you qualify, you can get that extra dose and the flu shot on the same day.

The delta variant is making me anxious about going to the doctor's office or pharmacy for a flu shot this year. Are there other choices?

If you're concerned, aim for an off hour and call to make sure the provider (as well as you) will be masked. If you're still worried, check with local clinics to see if there are any outdoor flu shot clinics in your area.

How do I make sure I get the right flu shot for me and my family?

"While the most important thing is to get any flu shot, there are some specialized flu shots for specific groups," says Pavia. The key is usually age.

Kids 8 and younger who are getting the flu shot for the first time need two doses, given a month apart, says Dr. Flor Munoz-Rivas, a pediatric infectious disease specialist at Baylor College of Medicine. Strong immunity doesn't kick in until two weeks after the second shot, "so parents should be scheduling these shots now," she says.

Immune systems weaken with age. That's why the CDC recommends that adults 65 and older get vaccinated with one of two souped-up flu shots: either the Fluzone High-Dose Quadrivalent vaccine or the FLUAD Quadrivalent vaccine. Both are designed to elicit a more robust immune response. If neither is available, then any flu shot is a good choice.

I'm pregnant. Should I get a flu shot?

Yes. And if you're in your third trimester, the CDC advises you get a flu shot ASAP so you can pass on the protection to your newborn from Day 1. "Babies can't get the flu shot until they are 6 months old but are protected by their mother's antibodies from a flu shot — if she gets the shot — until 6 months, when they can get their own flu vaccine," says Grohskopf. Just be sure to get the shot, not the nasal spray.

I have an allergy to eggs and heard I can't get a flu shot. Is that true?

Not really, says the CDC's Grohskopf.

It's true that most flu shots and one nasal spray flu vaccine approved by the Food and Drug Administration are manufactured using egg-based technology, so they contain a small amount of egg proteins. But studies of both the nasal spray and the shots found that allergic reactions are very rare.

Two egg-free vaccines are available: Flublok Quadrivalent (for people 18 and older) and Flucelvax Quadrivalent (which is approved for age 2 and up this season). But the CDC says people with a history of egg allergy can get any licensed, age-appropriate flu vaccine. If you have a history of severe allergic reaction to eggs, the CDC recommends you get your shot at a location where the staff can treat you if a rare allergic reaction does occur.

I'm willing to take my chances, so why should I get the flu vaccine?

With the pandemic still raging, skipping the flu shot is a much riskier proposition, says Dr. Bernard Camins, an infectious disease physician at the Mount Sinai Health System in New York City. "You could get the flu and need care but find hospitals overwhelmed because of COVID, or get the flu and get COVID. And especially if you are not vaccinated against the coronavirus, [you] run the risk of your immune system being overwhelmed by two viruses at the same time." Getting back-to-back infections could result in more serious illness, since the first infection may have already weakened your lungs, says Dr. Priya Nori, an infectious disease specialist at Albert Einstein College of Medicine.

If I'm already vaccinated against COVID-19, does getting the flu shot mean I'm doubly protected and no longer have to wear a mask?

Not at all. "Don't stop the public health measures," says Pavia. Distancing, wearing a mask and washing your hands, especially after coughs and sneezes, can improve the chances that you and others will not get the flu — or COVID-19.

Copyright NPR 2021.