Health officials warned that they expect a severe winter flu season and urged the country to get flu shots in addition to the latest COVID booster shot.

Australia and other Southern Hemisphere countries are currently experiencing severe flu seasons and the U.S. is expected to have a record flu season as cases in the northern regions continue to increase, prompting the warning and recommendations come from the Centers for Disease Control and Prevention.

The latest COVID booster from Pfizer is authorized for people 12-years-old and older and the Moderna shot is authorized for people 18 and older.

The nation's leading infectious disease expert, Dr. Anthony Fauci, has said that the booster shots may likely need to be administered once a year because COVID variants emerge and vaccination protection wanes.

The once-a-year schedule, health experts believe, would allow the booster and the flu shot to be administered at the same time.

The rollout of the upgraded COVID booster began earlier this month and its widely available in pharmacies healthcare clinics and doctor's offices.

Health experts say that getting the COVID booster and flu shot at the same time is safe and many locations are promoting the two shots at once.

Booster shots should be administered at least two months after that last vaccine dose or most recent booster shot, the CDC said. The agency also recommends that people wait at least three months before getting the booster if they have tested positive for the virus recently.

"It's clear that whether you're vaccinated, or you've had COVID, if you get this booster, you will get much higher levels of antibody and they are thought to help us get more prolonged protection," Dr. William Schaffner, a professor in the Division of Infectious Diseases at Vanderbilt University Medical Center, told CNN.

"The other thing that happens is that the immune system responds more broadly, and it looks as though we will get more broad coverage against other variants," he added.

Flu shots are being recommended by the CDC in the same schedule as last influenza season, with shots administered in September and October. The agency said on its website that everyone 6 months or older should get the flu shot every season, especially those that are at high risk for complications from influenza including individuals that are 65 or older, have chronic health conditions, or are pregnant.

"The ideal time is during the month of October and maybe the first couple of weeks of November – and the reason I say that is, particularly for older people and people who are frail, that will help their protection extend well through February into March, and that's when flu often peaks in the United States in February," Schaffner told the news outlet. "Everyone ages 6 months and older should get influenza vaccine."

Side effects from the flu vaccine, according to the CDC, can include soreness, redness or swelling at the vaccine site, low-grade headache, fever, muscle aches, nausea, and fatigue. Nasal spray doses can also include symptoms of runny nose, headache, sore throat, and cough in adults. Children may also experience vomiting, muscle aches, low-grade fever, and wheezing.

The side effects from a COVID booster shot can vary from person to person, with the most common symptoms, including fever, headache, fatigue, and pain at the injection.

COVID and flu symptoms are similar. The CDC says that a person who has COVID may have symptoms for two to 14 days, while the flu typically lasts one to four days after infection.

The flu and COVID share symptoms such as fever, chills, cough, shortness of breath or difficulty breathing, fatigue, sore throat, runny or stuffy nose, muscle pain or body aches, headache, vomiting, diarrhea, or change or loss of taste smell.