As more farm workers get sick with avian influenza, the US federal government is putting $72 million toward strengthening its vaccine stockpile.

The H5N1 virus has affected millions of wild and commercial birds nationwide, and in March it made the jump to dairy cows for the first time. As the number of affected animals grows, so does the concern for spread to people. In the past, H5N1 has had a high mortality rate in humans, and scientists are monitoring the virus closely to determine whether it poses a pandemic risk. The US government has a stockpile of approved H5N1 vaccines, but today’s awards, which will go to CSL Seqirus, GSK, and Sanofi, will double that number.

“We do expect that we will have a total of just over 10 million doses filled and finished by the end of the first quarter of calendar year 2025,” said David Boucher, director of infectious disease preparedness and response at the Administration for Strategic Preparedness and Response, in a press briefing on Friday.

Moderna, Pfizer, and GSK are also working on mRNA vaccines for bird flu, but those need to go through human testing and be approved by the US Food and Drug Administration before they could be used.

This year, 16 people in the US have been infected with bird flu. The US Centers for Disease Control and Prevention confirmed the latest two cases, both in California, Thursday evening. The individuals are farm workers who had contact with infected dairy cows at two facilities in the Central Valley, the epicenter of the state’s cattle outbreak. Both had mild symptoms, including eye redness, and are being treated with antiviral medication.