The Department of Health and Human Services (HHS), of which the CDC is part, believes the current bird flu outbreak has pandemic potential. Though person-to-person spread hasn’t yet been detected, H5N1 has infected 67 people in 10 states, including a death in Louisiana. That’s in addition to infection in more than 136 million poultry, nearly 11,000 wild birds, and over 900 dairy cattle as of mid-January. To that end, HHS has granted Moderna $590 million to help accelerate the development of a bird flu vaccine.

The agency announced its backing of the Massachusetts-based pharmaceutical firm about 72 hours before President Donald Trump was sworn in for his second term. (Robert F. Kennedy Jr., a vocal vaccine skeptic, is Trump’s pick to head HHS.) However, the partnership isn’t new. The Biomedical Advanced Research and Development Authority (BARDA), part of the HHS Administration for Strategic Preparedness and Response (ASPR), supplied the funding and has been working with Moderna since 2023 to develop mRNA vaccines for use during influenza-related public health emergencies. This latest financial support comes on top of the $176 million BARDA gave Moderna last summer.

“Avian flu variants have proven to be particularly unpredictable and dangerous to humans in the past. That is why this response has been a top priority for the Biden-Harris Administration and HHS,” outgoing HHS Secretary Xavier Becerra said in a Jan. 17 news release. “Accelerating the development of new vaccines will allow us to stay ahead and ensure that Americans have the tools they need to stay safe.”

HHS bets on mRNA vaccines for future pandemics

You likely hadn’t heard of mRNA vaccines before the COVID-19 pandemic. Moderna and Fortune 500 competitor Pfizer’s messenger RNA COVID vaccines were the first of their kind to be FDA-approved for human use. Moderna’s Dr. Doran Fink, clinical therapeutic area head for gastrointestinal and bacterial pathogens, explained to Fortune earlier this month how they differ from other vaccines you may have received.

“With [traditional] protein-based vaccines, the vaccines contain a protein that is typically produced by bacteria or yeast that are grown up in culture, and then the proteins are purified from that culture,” Fink said. “That protein is injected into the muscle or the tissue just under the skin, where it comes into contact with immune cells that then create the response that provides protection. For the mRNA vaccines, we don’t have the protein.”

Because mRNA vaccines instruct your body to make proteins that trigger immune responses rather than rely on weakened or inactivated viruses, they can be developed and updated more quickly. HHS said its award to Moderna was, in part, to “enhance mRNA platform capabilities.”

“The award made today is part of the ASPR’s commitment to strengthening pandemic preparedness through investments in innovative technology such as mRNA vaccines,” then–Assistant Secretary for Preparedness and Response Dawn O’Connell said in the news release. “mRNA technology will complement existing vaccine technology, allowing us to move faster and better target emerging viruses to protect Americans against future pandemics.”

Last year, Moderna completed a Phase I/II clinical trial of an investigational influenza vaccine called mRNA-1018, which was tested against H5 and H7 bird flu subtypes. The company said in a Jan. 17 news release that the early-stage trial produced “positive preliminary data” that would be shared at an unspecified “upcoming scientific meeting.” A Phase III trial for mRNA-1018 is planned.

Another Phase III trial will target H7N9, according to HHS. In order to combat “multiple health threats,” the agency added that Moderna will design up to four additional pandemic influenza vaccines for testing in Phase I clinical trials.

Seasonal flu shot as a tool in pandemic prevention

It may sound like something out of a sci-fi flick, but it’s possible for H5N1 to swap genetic material with a human seasonal flu virus and spawn a new form of influenza with pandemic potential. That’s why the CDC encourages everyone 6 months and older to get their annual flu shot—even though it won’t specifically protect them from bird flu.

Coinfection with bird and seasonal flu viruses is rare, the CDC says, and that risk will further lessen the more people get immunized. As of the week ended Jan. 4, less than half of U.S. adults (43.4%) and children (42.9%) had received the 2024–25 seasonal influenza shot.

For more on bird flu:

• Can you get bird flu from eating eggs? What you need to know about staying safe
• Experts sound the alarm as Ohio farmworker’s bird flu sparks fear it’s the next pandemic
• Bird flu FAQ: Everything you need to know about the latest H5N1 outbreak
• What are the symptoms of bird flu, and how does it spread?
• Bird flu could merge with seasonal flu to make mutated virus that could spread among humans, CDC warns