The last two flu seasons in the U.S. were mercifully mild—one of the few silver linings of the pandemic, as COVID-19 mitigation measures likely also prevented many cases of influenza.
However, our luck could run out in this year’s flu season. Australia, which often serves as an (imperfect) predictor of what’s to come for the U.S., has had its worst flu season in half a decade this year, CNN reports. Flu season also started early in Australia this year, another possible harbinger of what’s to come in the Northern Hemisphere.
Dr. Alicia Fry, chief of the epidemiology and prevention branch within the U.S. Centers for Disease Control and Prevention’s (CDC) influenza division, cautions that “if you’ve seen one flu season, you’ve seen one flu season”—meaning the virus is unpredictable and guesses about it aren’t always accurate. “Whether it will be a severe season or a mild season, or what to expect, or what viruses might circulate—that we really just don’t know,” Fry says.
Nonetheless, there are some factors that could set up the U.S. for a more serious flu season this year, says Dr. Brandon Webb, an infectious disease specialist at Utah’s Intermountain Medical Center. Influenza season severity can vary greatly from one year to the next, according to factors such as immunity and strain of influenza. “Individuals who get influenza the year prior probably carry over some incomplete or partial immunity,” Webb explains. Since few people got infected during the past two flu seasons, “we’re looking at globally, and especially in the U.S., record low community immunity levels to influenza.”
Fry states that relaxing COVID-19’s mitigation measures such as masking and social distancing could allow the flu to spread just like before.
Learn More: You Can Still Get Long COVID If You’re Vaccinated and Boosted
Webb warns that the possibility of heavy flu seasons colliding with SARS-CoV-2 is a concern for the country’s health care system. “If we have even a moderate-to-high influenza season that generates 300,000 or 400,000 hospitalizations and are also having to deal with a fall or winter COVID wave, that could put a strain on hospital systems around the country,” he says.
Fry suggests that people should get their vaccines sooner than they do later.
Federal health officials recommended on Sept. 1 that all people aged 12 or older receive a bivalent COVID-19 boost. This booster targets Omicron variants currently in circulation. Adolescents, teens, and adults over two months from the last COVID-19 dose can get updated shots. Experts recommend that you wait a bit longer. The CDC suggests that flu shots be administered by October 31st.
“If a person wants to get both at the same time, they can,” Fry says. White House COVID-19 Response Coordinator Ashish Jha agreed with Fry in a September 6 press briefing. “I really believe this is why God gave us two arms—one for the flu shot and the other one for the COVID shot,” he said.
Dual protection against COVID-19 as well as the flu may become easier in the future. Moderna and Novavax vaccine manufacturers are currently working together to develop shots that can target both influenza viruses through one shot. It’s not clear if or when these combination shots might be available, but their development offers a glimpse into what living with both COVID-19 and influenza may look like moving forward.
Many unknowns remain about even this year’s looming flu season. Webb suggests keeping an eye on influenza and COVID-19 rates, and making sure to take precautions. Wearing a mask while incrowded environments is advisable for people at high risk for severe breathing disease such as the elderly and patients with chronic conditions.
At least one thing makes Webb optimistic about this year’s flu season: Despite all the talk of pandemic fatigue, he thinks there’s been a cultural shift in the way people manage infectious diseases.
“People are, in general, much more aware now about the importance of infection control,” Webb says. “I would hope that we have a different culture in terms of recognizing that when you’re ill, it’s best to stay home.”
Here are more must-read stories from TIME