Doctors urge flu shots in light of COVID-19. Here's what you need to know.

Health experts have urged Americans to get their flu shots this year to help ward off a "twindemic."

"There's considerable concern as we enter the fall and the winter months and into the flu season that we'll have that dreaded overlap" of COVID-19 and the flu, the nation's top infectious disease expert, Dr. Anthony Fauci, said earlier this month.

The U.S. is battling a fresh surge of new coronavirus cases as winter approaches, and hospitals in some western and Midwestern states are filling up with COVID patients. The new rise follows an outbreak of COVID-19 cases that hit the Northeast hard earlier this year, followed by a rise in cases in the South over the summer.

"We far surpassed what we're used to with the flu with COVID this spring," said Dr. Stephanie Sterling, chief of infectious disease at NYU Langone Hospital–Brooklyn, in New York. "And to consider COVID plus flu together, this kind of pandemic would be devastating for communities and for healthcare systems."

She said we need to do everything we can to prevent the flu.

"We don't want a bad influenza season coinciding with a second wave of COVID," Sterling said. "Flu shots are safe. They do help prevent illness."

Why is getting a flu shot so important this year?

"One is to prevent flu illnesses and it's complications, but the benefit in this current season are resources that would otherwise be needed to care for patients with the flu that would become scarce, could be directed toward the pandemic," said Dr. Ram Koppaka, a medical officer for the CDC's National Center for Immunization and Respiratory Diseases.

The CDC estimates that last flu season, there were 38 million flu illnesses, 400,000 flu hospitalizations and 22,000 flu deaths. Koppaka said there were also 188 pediatric deaths from influenza.

An estimated 48% of U.S. adults and 64% of children received a flu vaccine during the same season. Koppaka said the number of flu vaccinations had been increasing prior to COVID-19, but there was still a need for improvement.

Sterling said that despite communities having a good amount of flu vaccinations, emergency rooms and hospital beds are often overwhelmed during a normal flu season.

This could be a great concern for hospitals in rural areas. Many rural hospitals have limited beds and ventilators, and rural Americans may be at higher risk of getting severely ill from COVID-19 due to a range of factors, according to the CDC.

Additionally, the body does not do well fighting two infections at the same time, according to Dr. Jacqueline P. Cooke, a hospitalist at Jefferson Health in New Jersey.

"The danger with COVID-19 is that the viral infection leads to overwhelming pneumonia and that type of viral pneumonia is what is causing the vast majority of people to need respiratory assistance and ventilation," she said.

Who should get a flu shot?

The CDC encourages people six months of age and older to get an annual flu shot. There are different types of vaccines that are age appropriate and for people with allergies.

Koppaka said September and October are favorable months for getting the flu vaccine, before flu outbreaks spread, however vaccinations can be given any time during the flu season. The time and length of the flu season fluctuates, but usually peeks between December and February and can last until May.

Sterling said it might be difficult determining if a patient's symptoms are from the flu, COVID-19 or medications. She said anyone experiencing respiratory illnesses this fall or winter should first talk to a doctor and test for both COVID-19 and the flu.

A flu shot could limit confusion and potentially assist doctors in diagnosis.

"The flu vaccine reduces the risk of developing influenza and therefore could point the healthcare provider in the direction of suspecting COVID-19 in somebody that presents with those types of symptoms," Koppaka said. "It would still become necessary for that healthcare provider to order diagnostic testing to be able to determine definitively which of the two viruses is the cause of the illness that they are faced with."

Where can you go to get a flu shot?

Flu shots are available at private doctors offices, urgent care centers, health clinics and pharmacies.

Natalie Nasca, 62, of Brooklyn and her friend received their vaccinations in mid-October at a free flu shot event at NYU Langone Health–Cobble Hill.

"Especially this year, with COVID, we made a point of getting out and getting our flu shot because we want to do everything to help keep New York's numbers low and down," said Nasca.

Allan Weiss, 79, of Brooklyn said he has gone to the event for the past several years and hasn't had an adverse effect.

"It can't hurt and it can only help," he said.

What are possible side effects?

Cooke said a person might feel sore or have a slightly elevated temperature following a flu shot.

The CDC adds nausea and fatigue as common side effects. More serious allergic reactions that could be life-threatening, such as hives, dizziness, breathing problems or an increased heartbeat, are rare, but effective treatments are available.

How much does a flu shot cost?

While most are free, some pharmacies charge between $39 and $73 without insurance.

A Walgreens media representative said there is a $0 copay for most insurance plans, and that the flu shot costs nothing for those enrolled in Medicare Part B, and for many with Medicaid. The representative said they also distribute 200,000 vouchers annually to various charities nationwide. Members of the Walgreens Prescriptions Savings Club receive 20% off the cash retail price of flu shots.

Are there enough flu shots to go around this year?

Last spring, the CDC started to prepare for a "more important than ever flu vaccination season," by working with industry partners to make sure enough flu vaccines would be available this season.

The CDC projects between 194 and 198 million doses of flu vaccines will be available for this year's flu season, about 12% higher than last year.

CVS and Walgreens representatives said they're seeing increased demand nationwide and are prepared with enough supplies.

CVS has "substantial inventory" of vaccinations, said spokesman Matt Blanchette. CVS recently administered the "9 millionth flu shot of the season, equaling the total amount given last season," he said. An appointment is not required but encouraged.

Alex Brown with Walgreens Corporate Media Relations said they administered 60% more flu shots this year compared to the same time last year. Brown said Walgreens has never administered this many flu shots this early in the season.

Walgreens also accepts walk-ins or patients can schedule an appointment.

Rite Aid has seen "consistent traffic of customers seeking flu shots" this fall, spokesman Christopher Savarese said.

Some places, however, have faced short supply. The Oneida County Health Department in Wisconsin announced on their website last week that public health flu clinics were canceled until further notice due to a shortage of vaccines.

Eric Nickens, Jr., a public information officer for DeKalb County Board of Health in Georgia, said they do not have a supply issue but that surrounding counties such as Gwinnett, Newton and Rockdale have a limited supply of the high-dose vaccine for people 65 and older.

Georgia Department of Public Health "has been told that when we get all the vaccine we pre-ordered, it's done, the manufacturers are not making more," said Nancy Nydam, the health department's director of communications.

She advised people needing the high-dose vaccine to call ahead to make sure supplies are available.

"If they cannot find high-dose, get a flu shot anyway," Nydam said. "The flu shot is designed to protect against four different flu viruses, including two influenza A viruses and two influenza B viruses."

Flu activity is currently low in the U.S., but is expected to increase in coming weeks.

The CDC recommends wearing a mask, washing hands, and staying 6 feet apart to slow the spread of COVID-19. Cooke believes wearing a mask could also help prevent the spread of the flu.

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