Flu season is on the horizon, while the coronavirus continues to spread with alarming speed. But what happens when the two germs collide?

It’s difficult to predict what this year’s flu season will look like, but Moderna, the company behind one of the nation’s three COVID-19 vaccines, is attempting to make the what-ifs a bit more predictable.

Moderna announced Thursday it is planning to create a single-dose vaccine that serves as a booster against both COVID-19 and the influenza virus as part of its “novel respiratory vaccine program.”

The vaccine will not be ready for this year’s flu season, which some experts predict could be worse than last year’s. The 2020 influenza season was virtually nonexistent, likely because most of the country was participating in coronavirus preventive measures that curbed the spread of other respiratory viruses.

What’s more, hospitals may still be overloaded with COVID-19 patients this fall, taking up much needed space for people critically sick with the flu, The Wall Street Journal reported. And some experts fear the season could begin earlier and cause more severe illness because people haven’t “been able to build up their natural immune defenses.”

It’s unclear if the coronavirus will become endemic, meaning it will keep spreading throughout communities without major outbreaks, such as the flu and common cold. If it does, COVID-19 vaccination will likely become a yearly norm.

“What we’re trying to do at Moderna actually is to get a flu vaccine in the clinic this year and then combine our flu vaccine to our COVID vaccine so you only have to get one boost at your local CVS store ... every year that would protect you [from] the variant of concern against COVID and the seasonal flu strain,” Moderna CEO Stephane Bancel previously said, according to CNBC.

White House health officials announced Aug. 18 they are recommending booster COVID-19 shots for all adult Americans to maximize and prolong protection against severe disease and death.

Under the plan, people could get booster shots beginning the week of Sept. 20, at least eight months after receipt of their second dose of two-dose shots. The final decision, however, is still pending authorization from the U.S. Food and Drug Administration and a recommendation from the Centers for Disease Control and Prevention.

The FDA is hosting a virtual advisory committee meeting to discuss Pfizer’s application for COVID-19 vaccine booster shots on Sept. 17.

People with weakened immune systems can currently get a third dose.